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fixed incorrect tags

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This commit is contained in:
Vijay Dev
2011-08-03 19:11:22 +05:30
committed by Xavier Noria
parent ff0b1a3cc6
commit 5adb90a14f
1 changed files with 16 additions and 16 deletions
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32
railties/guides/source/migrations.textile
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@@ -477,7 +477,7 @@ Several methods are provided that allow you to control all this:
For example, this migration
<pre>
<ruby>
class CreateProducts < ActiveRecord::Migration
def change
suppress_messages do
@@ -496,7 +496,7 @@ class CreateProducts < ActiveRecord::Migration
end
end
end
</pre>
</ruby>
generates the following output
@@ -525,7 +525,7 @@ Bob goes on vacation.
Alice creates a migration for the +products+ table which adds a new column and initializes it.
She also adds a validation to the Product model for the new column.
<pre>
<ruby>
# db/migrate/20100513121110_add_flag_to_product.rb
class AddFlagToProduct < ActiveRecord::Migration
@@ -534,19 +534,19 @@ class AddFlagToProduct < ActiveRecord::Migration
Product.all.each { |f| f.update_attributes!(:flag => 'false') }
end
end
</pre>
</ruby>
<pre>
<ruby>
# app/model/product.rb
class Product < ActiveRecord::Base
validates_presence_of :flag
end
</pre>
</ruby>
Alice adds a second migration which adds and initializes another column to the +products+ table and also adds a validation to the Product model for the new column.
<pre>
<ruby>
# db/migrate/20100515121110_add_fuzz_to_product.rb
class AddFuzzToProduct < ActiveRecord::Migration
@@ -555,16 +555,16 @@ class AddFuzzToProduct < ActiveRecord::Migration
Product.all.each { |f| f.update_attributes! :fuzz => 'fuzzy' }
end
end
</pre>
</ruby>
<pre>
<ruby>
# app/model/product.rb
class Product < ActiveRecord::Base
validates_presence_of :flag
validates_presence_of :fuzz
end
</pre>
</ruby>
Both migrations work for Alice.
@@ -575,12 +575,12 @@ Bob comes back from vacation and:
The migration crashes because when the model attempts to save, it tries to validate the second added column, which is not in the database when the _first_ migration runs.
<pre>
<plain>
rake aborted!
An error has occurred, this and all later migrations canceled:
undefined method `fuzz' for #<Product:0x000001049b14a0>
</pre>
</plain>
A fix for this is to create a local model within the migration. This keeps rails from running the validations, so that the migrations run to completion.
@@ -588,7 +588,7 @@ When using a faux model, it's a good idea to call +Product.reset_column_informat
If Alice had done this instead, there would have been no problem:
<pre>
<ruby>
# db/migrate/20100513121110_add_flag_to_product.rb
class AddFlagToProduct < ActiveRecord::Migration
@@ -600,9 +600,9 @@ class AddFlagToProduct < ActiveRecord::Migration
Product.all.each { |f| f.update_attributes!(:flag => false) }
end
end
</pre>
</ruby>
<pre>
<ruby>
# db/migrate/20100515121110_add_fuzz_to_product.rb
class AddFuzzToProduct < ActiveRecord::Migration
@@ -614,7 +614,7 @@ class AddFuzzToProduct < ActiveRecord::Migration
Product.all.each { |f| f.update_attributes! :fuzz => 'fuzzy' }
end
end
</pre>
</ruby>
h3. Schema Dumping and You