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docs, refactor docs about column modifiers. [ci skip] [Matthew Draper & Yves Senn]

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This is a follow up to #15602 which rendered the guides in a weird state:

  >  You can also specify some options just after the field type between curly
     braces. You can use the following modifiers:

  >  `null`         Allows or disallows `NULL` values in the column.

  >  NOTE: `null` and `default` cannot be specified via command line.

The modifiers are now moved into a separate section. The generator
simply referes to that section.

Related to #15583.

/cc @JuanitoFatas
This commit is contained in:
Yves Senn 2014-06-10 10:21:15 +02:00
parent 90fb179cb3
commit fcd0ac066e
1 changed files with 20 additions and 12 deletions
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32
guides/source/active_record_migrations.md
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@ -293,19 +293,10 @@ end
You can append as many column name/type pairs as you want.
### Supported Type Modifiers
### Passing Modifiers
You can also specify some options just after the field type between curly
braces. You can use the following modifiers:
* `limit` Sets the maximum size of the `string/text/binary/integer` fields.
* `precision` Defines the precision for the `decimal` fields, representing the total number of digits in the number.
* `scale` Defines the scale for the `decimal` fields, representing the number of digits after the decimal point.
* `polymorphic` Adds a `type` column for `belongs_to` associations.
* `null` Allows or disallows `NULL` values in the column.
* `default` Allows to set a default value on the column. NOTE: If using a dynamic value (such as date), the default will only be calculated the first time (e.g. on the date the migration is applied.)
NOTE: `null` and `default` cannot be specified via command line.
Some commonly used [type modifiers](#column-modifiers) can be passed directly on
the command line. They are enclosed by curly braces and follow the field type:
For instance, running:
@ -324,6 +315,8 @@ class AddDetailsToProducts < ActiveRecord::Migration
end
```
TIP: Have a look at the generators help output for further details.
Writing a Migration
-------------------
@ -441,6 +434,21 @@ change_column_default :products, :approved, false
This sets `:name` field on products to a `NOT NULL` column and the default
value of the `:approved` field to false.
### Column Modifiers
Column modifiers can be applied when creating or changing a column:
* `limit` Sets the maximum size of the `string/text/binary/integer` fields.
* `precision` Defines the precision for the `decimal` fields, representing the total number of digits in the number.
* `scale` Defines the scale for the `decimal` fields, representing the number of digits after the decimal point.
* `polymorphic` Adds a `type` column for `belongs_to` associations.
* `null` Allows or disallows `NULL` values in the column.
* `default` Allows to set a default value on the column. NOTE: If using a dynamic value (such as date), the default will only be calculated the first time (e.g. on the date the migration is applied.)
* `index` Adds an index for the column.
Some adapters may support additional options; see the adapter specific API docs
for further information.
### When Helpers aren't Enough
If the helpers provided by Active Record aren't enough you can use the `execute`