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separated customization documentation from main README
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John Mair
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README.markdown
368
README.markdown
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@ -266,373 +266,7 @@ Customizing Pry
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Pry supports customization of the input, the output, the commands,
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the hooks, the prompt, and 'print' (the "P" in REPL).
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Global customization, which applies to all Pry sessions, is done
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through invoking class accessors on the `Pry` class, the accessors
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are:
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* `Pry.input=`
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* `Pry.output=`
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* `Pry.commands=`
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* `Pry.hooks=`
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* `Pry.prompt=`
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* `Pry.print=`
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Local customization (applied to a single Pry session) is done by
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passing config hash options to `Pry.start()` or to `Pry.new()`; also the
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same accessors as described above for the `Pry` class exist for a
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Pry instance so that customization can occur during runtime.
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### Input
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For input Pry accepts any object that implements the `readline` method. This
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includes `IO` objects, `StringIO`, `Readline` and custom objects. Pry
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initially defaults to using `Readline` for input.
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#### Example: Setting global input
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Setting Pry's global input causes all subsequent Pry instances to use
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this input by default:
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Pry.input = StringIO.new("@x = 10\nexit")
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Object.pry
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Object.instance_variable_get(:@x) #=> 10
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The above will execute the code in the `StringIO`
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non-interactively. It gets all the input it needs from the `StringIO`
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and then exits the Pry session. Note it is important to end the
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session with 'exit' if you are running non-interactively or the Pry
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session will hang as it loops indefinitely awaiting new input.
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#### Example: Setting input for a specific session
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The settings for a specific session override the global settings
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(discussed above). There are two ways to set input for a specific pry session: At the
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point the session is started, or within the session itself (at runtime):
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##### At session start
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Pry.start(Object, :input => StringIO.new("@x = 10\nexit"))
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Object.instance_variable_get(:@x) #=> 10
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##### At runtime
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If you want to set the input object within the session itself you use
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the special `_pry_` local variable which represents the Pry instance
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managing the current session; inside the session we type:
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_pry_.input = StringIO.new("@x = 10\nexit")
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Note we can also set the input object for the parent Pry session (if
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the current session is nested) like so:
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_pry_.parent.input = StringIO.new("@x = 10\nexit")
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### Output
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For output Pry accepts any object that implements the `puts` method. This
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includes `IO` objects, `StringIO` and custom objects. Pry initially
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defaults to using `$stdout` for output.
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#### Example: Setting global output
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Setting Pry's global output causes all subsequent Pry instances to use
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this output by default:
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Pry.output = StringIO.new
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#### Example: Setting output for a specific session
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As per Input, given above, we set the local output as follows:
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##### At session start
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Pry.start(Object, :output => StringIO.new("@x = 10\nexit"))
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##### At runtime
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_pry_.output = StringIO.new
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### Commands
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Pry commands are not methods; they are commands that are intercepted
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and executed before a Ruby eval takes place. Pry comes with a default
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command set (`Pry::Commands`), but these commands can be augmented or overriden by
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user-specified ones.
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The Pry command API is quite sophisticated supporting features such as:
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command set inheritance, importing of specific commands from another
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command set, deletion of commands, calling of commands within other
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commands, and so on.
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A valid Pry command object must inherit from
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`Pry::CommandBase` (or one of its subclasses) and use the special command API:
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#### Example: Defining a command object and setting it globally
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class MyCommands < Pry::CommandBase
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command "greet", "Greet the user." do |name|
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output.puts "Hello #{name.capitalize}, how are you?"
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end
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end
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Pry.commands = MyCommands
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Then inside a pry session:
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pry(main)> greet john
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hello John, how are you?
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=> nil
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#### Example: Using a command object in a specific session
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As in the case of `input` and `output`:
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##### At session start:
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Pry.start(self, :commands => MyCommands)
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##### At runtime:
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_pry_.commands = MyCommands
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#### The command API
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The command API is defined by the `Pry::CommandBase` class (hence why
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all commands must inherit from it or a subclass). The API works as follows:
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##### `command` method
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The `command` method defines a new command, its parameter is the
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name of the command and an optional second parameter is a description of
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the command.
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The associated block defines the action to be performed. The number of
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parameters in the block determine the number of parameters that will
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be sent to the command (from the Pry prompt) when it is invoked. Note
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that all parameters that are received will be strings; if a parameter
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is not received it will be set to `nil`.
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command "hello" do |x, y, z|
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puts "hello there #{x}, #{y}, and #{z}!"
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end
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Command aliases can also be defined - simply use an array of strings
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for the command name - all these strings will be valid names for the
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command.
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command ["ls", "dir"], "show a list of local vars" do
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output.puts target.eval("local_variables")
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end
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##### `delete` method
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The `delete` method deletes a command or a group of a commands; it
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can be useful when inheriting from another command set when you decide
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to keep only a portion of inherited commands.
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class MyCommands < Pry::Commands
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delete "show_method", "show_imethod"
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end
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##### `import_from` method
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The `import_from` method enables you to specifically select which
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commands will be copied across from another command set, useful when
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you only want a small number of commands and so inheriting and then
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deleting would be inefficient. The first parameter to `import_from`
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is the class to import from and the other paramters are the names of
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the commands to import:
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class MyCommands < Pry::CommandBase
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import_from Pry::Commands, "ls", "status", "!"
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end
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##### `run` method
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The `run` command invokes one command from within another.
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The first parameter is the name of the command to invoke
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and the remainder of the parameters will be passed on to the command
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being invoked:
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class MyCommands < Pry::Commands
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command "ls_with_hello" do
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output.puts "hello!"
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run "ls"
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end
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end
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#### Utility methods for commands
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All commands can access the special `output` and `target` methods. The
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`output` method returns the `output` object for the active pry session.
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Ensuring that your commands invoke `puts` on this rather than using
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the top-level `puts` will ensure that all your session output goes to
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the same place.
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The `target` method returns the `Binding` object the Pry session is currently
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active on - useful when your commands need to manipulate or examine
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the state of the object. E.g, the "ls" command is implemented as follows
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command "ls" do
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output.puts target.eval("local_variables + instance_variables").inspect
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end
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#### The opts hash
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These are miscellaneous variables that may be useful to your commands:
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* `opts[:val]` - The line of input that invoked the command.
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* `opts[:eval_string]` - The cumulative lines of input for multi-line input.
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* `opts[:nesting]` - Lowlevel session nesting information.
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* `opts[:commands]` - Lowlevel data of all Pry commands.
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(see commands.rb for examples of how some of these options are used)
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#### The `help` command
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The `Pry::CommandBase` class automatically defines a `help` command
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for you. Typing `help` in a Pry session will show a list of commands
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to the user followed by their descriptions. Passing a parameter to
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`help` with the command name will just return the description of that
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specific command. If a description is left out it will automatically
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be given the description "No description.".
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If the description is explicitly set to `""` then this command will
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not be displayed in `help`.
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### Hooks
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Currently Pry supports just two hooks: `before_session` and
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`after_session`. These hooks are invoked before a Pry session starts
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and after a session ends respectively. The default hooks used are
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stored in the `Pry::DEFAULT_HOOKS` and just output the text `"Beginning
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Pry session for <obj>"` and `"Ending Pry session for <obj>"`.
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#### Example: Setting global hooks
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All subsequent Pry instances will use these hooks as default:
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Pry.hooks = {
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:before_session => proc { |out, obj| out.puts "Opened #{obj}" },
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:after_session => proc { |out, obj| out.puts "Closed #{obj}" }
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}
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5.pry
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Inside the session:
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Opened 5
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pry(5)> exit
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Closed 5
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Note that the `before_session` and `after_session` procs receive the
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current session's output object and session receiver as parameters.
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#### Example: Setting hooks for a specific session
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Like all the other customization options, the global default (as
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explained above) can be overriden for a specific session, either at
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session start or during runtime.
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##### At session start
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Pry.start(self, :hooks => { :before_session => proc { puts "hello world!" },
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:after_session => proc { puts "goodbye world!" }
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})
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##### At runtime
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_pry_.hooks = { :before_session => proc { puts "puts "hello world!" } }
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### Prompts
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The Pry prompt is used by `Readline` and other input objects that
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accept a prompt. Pry can accept two prompt-types for every prompt; the
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'main prompt' and the 'wait prompt'. The main prompt is always used
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for the first line of input; the wait prompt is used in multi-line
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input to indicate that the current expression is incomplete and more lines of
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input are required. The default Prompt used by Pry is stored in the
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`Pry::DEFAULT_PROMPT` constant.
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A valid Pry prompt is either a single `Proc` object or a two element
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array of `Proc` objects. When an array is used the first element is
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the 'main prompt' and the last element is the 'wait prompt'. When a
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single `Proc` object is used it will be used for both the main prompt
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and the wait prompt.
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#### Example: Setting global prompt
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The prompt `Proc` objects are passed the receiver of the Pry session
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and the nesting level of that session as parameters (they can simply
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ignore these if they do not need them).
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# Using one proc for both main and wait prompts
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Pry.prompt = proc { |obj, nest_level| "#{obj}:#{nest_level}> " }
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# Alternatively, provide two procs; one for main and one for wait
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Pry.prompt = [ proc { "ENTER INPUT> " }, proc { "MORE INPUT REQUIRED!* " }]
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#### Example: Setting the prompt for a specific session
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##### At session start
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Pry.start(self, :prompt => [proc { "ENTER INPUT> " },
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proc { "MORE INPUT REQUIRED!* " }])
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##### At runtime
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_pry_.prompt = [proc { "ENTER INPUT> " },
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proc { "MORE INPUT REQUIRED!* " }]
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### Print
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The Print phase of Pry's READ-EVAL-PRINT-LOOP can be customized. The
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default action is stored in the `Pry::DEFAULT_PRINT` constant and it
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simply outputs the value of the current expression preceded by a `=>` (or the first
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line of the backtrace if the value is an `Exception` object.)
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The print object should be a `Proc` and the parameters passed to the
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`Proc` are the output object for the current session and the 'value'
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returned by the current expression.
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#### Example: Setting global print object
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Let's define a print object that displays the full backtrace of any
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exception and precedes the output of a value by the text `"Output is: "`:
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Pry.print = proc do |output, value|
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case value
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when Exception
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output.puts value.backtrace
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else
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output.puts "Output is: #{value}"
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end
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end
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#### Example: Setting the print object for a specific session
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##### At session start
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Pry.start(self, :print => proc do |output, value|
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case value
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when Exception
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output.puts value.backtrace
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else
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output.puts "Output is: #{value.inspect}"
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end
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end)
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##### At runtime
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_pry_.print = proc do |output, value|
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case value
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when Exception
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output.puts value.backtrace
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else
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output.puts "Output is: #{value.inspect}"
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end
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end
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[Read how to customize Pry here.](https://github.com/banister/pry/wiki/Customizing-pry)
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Contact
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-------
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