the difference between for-loop and each

[Andreas S]

Hopefully (I'm sure) somebody can shed a light on this. This caught me by s=
urprise

test.rb:
TEST =3D []
def procs &block
TEST << block
end

#for n in [1,2,3] do
[1,2,3].each do |n|
procs do
puts "#{n}"
end
end

TEST.each do |t|
puts t
t.call
end

With for loop#
3
#
3
#
3

With each#
1
#
2
#
3

I thought for-loop behaves the same as each. Apparently not. Why is this an=
d is this a good thing?

Thank you in advance
-andre
_________________________________________________________________
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challenge with star power.
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t=

 

[Robert Klemme]

Hopefully (I'm sure) somebody can shed a light on this. This caught me by surprise

test.rb:
TEST = []
def procs &block
TEST << block
end

#for n in [1,2,3] do
[1,2,3].each do |n|
procs do
puts "#{n}"
end
end

TEST.each do |t|
puts t
t.call
end

With for loop#
3
#
3
#
3

With each#
1
#
2
#
3

I thought for-loop behaves the same as each. Apparently not. Why is this and is this a good thing?

The reason for the behavior you are seeing is different scoping. "for"
does not open a new scope while block parameters sit in a different
scope. Apart from that "for" is a keyword (i.e. part of the language)
while "each" is just a method like other methods.

irb(main):014:0> def f1(x) x.each {|y| p y}; p y end
=> nil
irb(main):015:0> def f2(x) for y in x; p y; end; p y end
=> nil
irb(main):016:0> f1 %w{foo bar baz}
"foo"
"bar"
"baz"
NameError: undefined local variable or method `y' for main:Object
from (irb):14:in `f1'
from (irb):16
from :0
irb(main):017:0> f2 %w{foo bar baz}
"foo"
"bar"
"baz"
"baz"
=> nil
irb(main):018:0>

I'd say it's a good thing because you get the choice - if you need the
iteration variable after the block then use "for" - otherwise use "each".

Kind regards

robert