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[ruby/csv] Recipes for field converters (#177)

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https://github.com/ruby/csv/commit/aea896f030
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Burdette Lamar 2020-09-20 16:38:40 -05:00 • committed by Sutou Kouhei
parent 98d52d873e
commit 4be336b1b7
Notes: git 2020-11-24 09:34:30 +09:00
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doc/csv/recipes.rdoc
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@ -1,5 +1,8 @@
== Recipes
All code snippets on this page assume that the following has been executed:
require 'csv'
=== Contents
- {Parsing: Source Formats}[#label-Parsing-3A+Source+Formats]
@ -12,6 +15,10 @@
- {Parse from IO Stream}[#label-Parse+from+IO+Stream]
- {Parse from IO Stream Without Headers}[#label-Parse+from+IO+Stream+Without+Headers]
- {Parse from IO Stream with Headers}[#label-Parse+from+IO+Stream+with+Headers]
- {Parsing: Field Converters}[#label-Parsing-3A+Field+Converters]
- {Convert Fields to Objects}[#label-Convert+Fields+to+Objects]
- {Convert Fields to Objects Using Built-In Converters}[#label-Convert+Fields+to+Objects+Using+Built-In+Converters]
- {Convert Fields to Objects Using Custom Converters}[#label-Convert+Fields+to+Objects+Using+Custom+Converters]
- {Generating: Output Formats}[#label-Generating-3A+Output+Formats]
- {Generate to String}[#label-Generate+to+String]
- {Generate to String Without Headers}[#label-Generate+to+String+Without+Headers]
@ -152,6 +159,52 @@ Output:
#<CSV::Row "Name":"bar" "Value":"1">
#<CSV::Row "Name":"baz" "Value":"2">
=== Parsing: Field Converters
==== Convert Fields to Objects
Use field converters to change parsed Strings into other, more specific, object.
==== Convert Fields to Objects Using Built-In Converters
Without converters (all fields parsed as Strings):
source = "0,1.1,2020-09-19"
parsed = CSV.parse(source)
parsed # => [["0", "1.1", "2020-09-19"]]
parsed.first.each {|field| p field.class }
Output:
String
String
String
With built-in converters (see {Built-In Field Converters}[../../CSV.html#class-CSV-label-Built-In+Field+Converters]):
parsed = CSV.parse(source, converters: :all)
parsed # => [[0, 1.1, #<DateTime: 2020-09-19T00:00:00+00:00 ((2459112j,0s,0n),+0s,2299161j)>]]
parsed.first.each {|field| p field.class }
Output:
Integer
Float
DateTime
==== Convert Fields to Objects Using Custom Converters
Define a custom field converter:
strip_converter = proc {|field| field.strip }
Without the new converter:
string = " foo , 0 \n bar , 1 \n baz , 2 \n"
array = CSV.parse(string)
array # => [[" foo ", " 0 "], [" bar ", " 1 "], [" baz ", " 2 "]]
With the new converter:
array = CSV.parse(string, converters: strip_converter)
array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
You can also register a custom field converter, then refer to it by name:
CSV::Converters[:strip] = strip_converter
array = CSV.parse(string, converters: :strip)
array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
=== Generating: Output Formats
==== Generate to \String Without Headers