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Fix errors for four of the code samples

The four code samples that fail to run are:

- Add attribute magic to objects. Fixed by introducing a Person
  instance variable.

- Tracking value changes. Fixed by replacing `attr_accessor` with
  `define_attribute_methods`, providing getter and setter methods
  for `name` and providing the missing `Person#save` method. A
  call to `Person#save` has to precede the `person.name = 'robert'`
  assignment, if we want `previous_changes` to include 'bob'.

- Adding `errors` interface to objects. Fixed by introducing a
  Person instance variable, assigning `nil` to its name and calling
  `Person#validate!`.

- Custom validators. Fixed by defining `HasNameValidator` before
  it is used by `ValidatorPerson`.

All the code samples can now be run smoothly.

Call Dirty#changes_applied in Person#save, instead of modifying instance vars.
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1 parent 1fbb905 commit f6ab778297350aa3dad1dbf23ccd2d8a74e3dab7 Peter Markou committed Mar 7, 2014
Showing with 49 additions and 30 deletions.
  1. +49 −30 activemodel/README.rdoc
@@ -49,7 +49,8 @@ behavior out of the box:
send("#{attr}=", nil)
end
end
-
+
+ person = Person.new
person.clear_name
person.clear_age
@@ -78,7 +79,21 @@ behavior out of the box:
class Person
include ActiveModel::Dirty
- attr_accessor :name
+ define_attribute_methods :name
+
+ def name
+ @name
+ end
+
+ def name=(val)
+ name_will_change! unless val == @name
+ @name = val
+ end
+
+ def save
+ # do persistence work
+ changes_applied
+ end
end
person = Person.new
@@ -88,6 +103,7 @@ behavior out of the box:
person.changed? # => true
person.changed # => ['name']
person.changes # => { 'name' => [nil, 'bob'] }
+ person.save
person.name = 'robert'
person.save
person.previous_changes # => {'name' => ['bob, 'robert']}
@@ -116,7 +132,10 @@ behavior out of the box:
"Name"
end
end
-
+
+ person = Person.new
+ person.name = nil
+ person.validate!
person.errors.full_messages
# => ["Name cannot be nil"]
@@ -180,41 +199,41 @@ behavior out of the box:
* Validation support
- class Person
- include ActiveModel::Validations
+ class Person
+ include ActiveModel::Validations
- attr_accessor :first_name, :last_name
+ attr_accessor :first_name, :last_name
- validates_each :first_name, :last_name do |record, attr, value|
- record.errors.add attr, 'starts with z.' if value.to_s[0] == ?z
- end
- end
+ validates_each :first_name, :last_name do |record, attr, value|
+ record.errors.add attr, 'starts with z.' if value.to_s[0] == ?z
+ end
+ end
- person = Person.new
- person.first_name = 'zoolander'
- person.valid? # => false
+ person = Person.new
+ person.first_name = 'zoolander'
+ person.valid? # => false
{Learn more}[link:classes/ActiveModel/Validations.html]
* Custom validators
+
+ class HasNameValidator < ActiveModel::Validator
+ def validate(record)
+ record.errors[:name] = "must exist" if record.name.blank?
+ end
+ end
+
+ class ValidatorPerson
+ include ActiveModel::Validations
+ validates_with HasNameValidator
+ attr_accessor :name
+ end
- class ValidatorPerson
- include ActiveModel::Validations
- validates_with HasNameValidator
- attr_accessor :name
- end
-
- class HasNameValidator < ActiveModel::Validator
- def validate(record)
- record.errors[:name] = "must exist" if record.name.blank?
- end
- end
-
- p = ValidatorPerson.new
- p.valid? # => false
- p.errors.full_messages # => ["Name must exist"]
- p.name = "Bob"
- p.valid? # => true
+ p = ValidatorPerson.new
+ p.valid? # => false
+ p.errors.full_messages # => ["Name must exist"]
+ p.name = "Bob"
+ p.valid? # => true
{Learn more}[link:classes/ActiveModel/Validator.html]

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