Attributes= operation *appends* instead of replacing for accepts_nested_attributes_for with has_many

When using “attributes=” for an object with a
accepts_nested_attributes_for
a model
that has a has_many relationship will cause the has_many array to be
appended-to
instead of being replaced as would be expected by a straight assignment
operation.

See this example:

class Member < ActiveRecord::Base
has_many :posts
accepts_nested_attributes_for :posts
end

class Post < ActiveRecord::Base
belongs_to :member
end

m=Member.new
p={:name => ‘joe’, :posts_attributes => [{:title=>‘t1’},{:title=>‘t2’}]}

m.attributes = p
m.posts.size ----> 2

m.attributes = p
m.posts.size ----> 4

Is this a feature or a bug? If it is a feature, how is it supposed to
be
used?

On Tuesday, February 26, 2013 7:35:23 PM UTC, xop wrote:

When using “attributes=” for an object with a accepts_nested_attributes_for a
model
that has a has_many relationship will cause the has_many array to be appended-to
instead of being replaced as would be expected by a straight assignment
operation.

attributes= has always behaved like that ( the name is bad - it’s not
really an accessor at all. The newer name is assign_attributes)

Fred

On Tuesday, 26 February 2013 14:35:23 UTC-5, xop wrote:

class Member < ActiveRecord::Base

m.attributes = p
m.posts.size ----> 2

m.attributes = p
m.posts.size ----> 4

Is this a feature or a bug? If it is a feature, how is it supposed to be
used?

With nested attributes, you’ll wind up creating new records unless the
entries in :posts_attributes have an :id key which indicates they’re
existing records to be updated.

–Matt J.

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