How to assign multiple attributes at once to an object in Ruby-CodePudding

I have an object Foo and want to assign multiple attributes to it at once, similar to assign_attributes in Rails:

class Foo
    attr_accessor :a, :b, :c
end

f = Foo.new
my_hash = {a: "foo", b: "bar", c: "baz"}
f.assign_attributes(my_hash)

The above does not work except if the class is an ActiveRecord Model in Rails. Is there any way to do it in Ruby?

CodePudding user response：

You can implement the mass-assignment method yourself.

One option is to set the corresponding instance variables via instance_variable_set:

class Foo
  attr_accessor :a, :b, :c

  def assign_attributes(attrs)
    attrs.each_pair do |attr, value|
      instance_variable_set("@#{attr}", value)
    end
  end
end

another way is to dynamically invoke the setters via public_send:

  def assign_attributes(attrs)
    attrs.each_pair do |attr, value|
      public_send("#{attr}=", value)
    end
  end

In addition, you might want to ensure that the passed argument is a hash and that its keys are valid / known attributes.

Using the latter approach conveys an advantage, in that if a setter has been defined to include constraints and controls on the value being set, the latter approach respects that.

CodePudding user response：

The assign_attributes is an instance method of ActiveRecord

You have to define your assign_attributes method if not using ActiveRecord

def assign_attributes(attrs_hash)
  attrs_hash.each do |k, v|
    self.instance_variable_set("@#{k}", v)
  end
end