Dynamic class instantiation by iteration

[Frisco Del Rosario]

I'm curious as to why the following does not create three instances of
class Cat:


class Cat
def initialize(name)
@name = name
end
end

toons = ["Felix", "Garfield", "Heathcliff"]

toons.each {|t| t = Cat.new(t)}


In irb, the last input and output are:

irb(main):008:0> toons.each {|t| t=Cat.new(t)}
=> ["Felix", "Garfield", "Heathcliff"]

which I don't understand.

 

[Stefano Crocco]

I'm curious as to why the following does not create three instances of
class Cat:


class Cat
def initialize(name)
@name = name
end
end

toons = ["Felix", "Garfield", "Heathcliff"]

toons.each {|t| t = Cat.new(t)}


In irb, the last input and output are:

irb(main):008:0> toons.each {|t| t=Cat.new(t)}
=> ["Felix", "Garfield", "Heathcliff"]

which I don't understand.

Your code does create three instances of Cat, but they're thrown away
immediately, since you don't use them. Array#each always return the receiver
(in your case, the array ["Felix", "Garfield", "Heathcliff"]), regardless of
the return value of the block. If you want to obtain an array with the three
instances of Cat, use Array#map instead:

cats = toons.map{|n| Cat.new(name)}

I hope this helps

Stefano

 

[David A. Black]

Hi --

I'm curious as to why the following does not create three instances of
class Cat:


class Cat
def initialize(name)
@name = name
end
end

toons = ["Felix", "Garfield", "Heathcliff"]

toons.each {|t| t = Cat.new(t)}


In irb, the last input and output are:

irb(main):008:0> toons.each {|t| t=Cat.new(t)}
=> ["Felix", "Garfield", "Heathcliff"]

which I don't understand.

Your code does create three instances of Cat, but they're thrown away
immediately, since you don't use them. Array#each always return the receiver
(in your case, the array ["Felix", "Garfield", "Heathcliff"]), regardless of
the return value of the block. If you want to obtain an array with the three
instances of Cat, use Array#map instead:

cats = toons.map{|n| Cat.new(name)}

Make that Cat.new(n)


David

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[Stefano Crocco]

Make that Cat.new(n)

Of course

Stefano

 

[Phillip Gawlowski]

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David A. Black wrote:

|
| Make that Cat.new(n)

Hm. Shouldn't that be Cat.mew(n)?

SCNR.

- --
Phillip Gawlowski
Twitter: twitter.com/cynicalryan
Blog: http://justarubyist.blogspot.com

You watch a talk show recently? They're doing one next month on a
normal, happy heterosexual couple, assuming they can find one.
~ -- Professor Ralph Noble, RPI, Psychology of Motivation, Fall 1991
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