I'm having a problem in ruby and I can't seem to find the solution even though I know it's somehow possible. I have a class and I want to assign some variables to it in a do block like so:
tester = Person.new
tester do
:name => 'Andy'
:example => 'Example'
end
puts "#{tester.name}:#{tester.example}" #Should output 'Andy:Example'
Has anyone got any ideas? I apologise for my terrible way of explaining. I'm new to Ruby :)
There's the good old yield self idiom for that too:
class Person
attr_accessor :name, :example
def initialize
yield self if block_given?
end
end
tester = Person.new do |p|
p.name = 'Andy'
p.example = 'Example'
end
puts "#{tester.name}:#{tester.example}"
yield self if block_given? :). Anyway this is not the way Ruby works. Actionscript has got its with method wich allows to work, you know, "in context" of its object. And you can't do this kind of job in Ruby.
with should be fairly easy to implement too :-)eval it's really trivial: gist.github.com/2146609 Of course having to use the self receiver is a bit ugly, but I don't have time to hack around that at the moment.You can't do it in Ruby this way. You should specify reciever
tester = Person.new
tester.name = "Andy"
tester.example = "Example"
PS
Here is related topic:
In Ruby, is there a way to accomplish what `with` does in Actionscript?
yield self idiom that gemspec files or Rake uses. See my answer :-)It may be set like this:
tester = Person.new.tap do |person|
person.name = 'John'
end
It is not possible to call a method whose name ends in = without a receiver, because doing so will create a new local variable. I suggest allowing new values to be passed to your reader methods:
class Person
def initialize(&block)
if block.arity.zero? then instance_eval &block
else block.call self end
end
def name(new_name = nil)
@name = new_name unless new_name.nil?
@name
end
end
Now you can write:
Person.new do
name 'Andy'
end
The only drawback to this approach is that it is impossible to set the attribute back to nil, so consider providing a conventional writer method as well.
do is refers to the object yielded from an iteration, which doesn't allow you to write code as above. I'd suggest a different approach:
class Person
attr_accessor :name, :example
def assign(props = {})
props.each{|prop, value| self.send("#{prop.to_s}=", value)}
self
end
end
x = Person.new
x.assign :name => "test", :example => "test_example"
=> #<Person:0x27a4760 @name="test", @example="test_example">
@fl00r's suggestion is right or you may do it this way which is most similar to him:
tester = Person.new
tester[:name] = "Andy"
tester[:example] = "Example"
Person class specifies a []= method, you'll get a NoMethodError.