Am new to Ruby and have the folloiwng Question.
I have a class, say Collect, and I want to mixin Enumerable. How do I
write the each method in Collect?
class Collect
include Enumerable
def initialize()
@array = Array.new(0)
@ct = 0
end
def add(item)
@array.push(item)
@ct += 1
end
def howmany
@ct
end
def each
Assuming you want to iterate over @array,
def each
@array.each {|i| yield i}
end
martin
On 8/1/06, Michael Saltzman <michael@trainingetc.com> wrote:
Am new to Ruby and have the folloiwng Question.
I have a class, say Collect, and I want to mixin Enumerable. How do I
write the each method in Collect?class Collect
include Enumerable
def initialize()
@array = Array.new(0)
@ct = 0
end
def add(item)
@array.push(item)
@ct += 1
end
def howmany
@ct
end
def each
#
# Not sure how to do this???
#
end
end
It depends what you want each to do? Just to wrap @array.each? In that case,
this would work:
def each
@array.each {|item| yield item}
end
Of course you can do whatever you want to the array item in the block before
you yield it again.
An alternative technique is as follows:
def each(&block)
@array.each(&block)
end
I'm sure someone will correct me if I describe this slightly wonky, but the
basic idea is that the interpreter converts the block argument to a proc with
a name (I think I read an article that claimed a block is always converted to
a proc, but when no &arg is given, it is simply a proc with no name,
accessible of course via yield). This is then passed on to @array.each as a
block argument.
I don't know whether there are any real advantages or disadvantages to either
method. Hope this helps
Alex
On Tuesday 01 August 2006 16:43, Michael Saltzman wrote:
Am new to Ruby and have the folloiwng Question.
I have a class, say Collect, and I want to mixin Enumerable. How do I
write the each method in Collect?class Collect
include Enumerable
def initialize()
@array = Array.new(0)
@ct = 0
end
def add(item)
@array.push(item)
@ct += 1
end
def howmany
@ct
end
def each
#
# Not sure how to do this???
#
end
end
Michael Saltzman wrote:
Am new to Ruby and have the folloiwng Question.
I have a class, say Collect, and I want to mixin Enumerable. How do I write the each method in Collect?
class Collect
include Enumerable
def initialize()
@array = Array.new(0)
@ct = 0
end
def add(item)
@array.push(item)
@ct += 1
end
def howmany
@ct
end
def each
#
# Not sure how to do this???
#
end
end
You have several options:
class Collect
include Enumerable
def initialize()
@array =
end
def add(item)
@array.push(item)
self
end
alias :<< :add
def howmany
@array.size
end
# option 1: use yield
def each_1
@array.each {|x| yield x}
self
end
# option 2: delegate to Array's each
def each_2(&b)
@array.each(&b)
self
end
end
Kind regards
robert
It depends what you want each to do? Just to wrap @array.each? In that
case, this would work:
def each
@array.each {|item| yield item}
endOf course you can do whatever you want to the array item in the block
before you yield it again.An alternative technique is as follows:
def each(&block)
@array.each(&block)
end
<snip>
I don't know whether there are any real advantages or disadvantages to
either method. Hope this helps
Just did a quick benchmark out of curiosity:
user system total real
Two yields 15.720000 2.220000 17.940000 ( 20.336562)
Pass the named block 4.130000 1.020000 5.150000 ( 5.562950)
Direct on attr_accessor 3.810000 1.010000 4.820000 ( 5.440259)
I passed the block {|i| i} and initialized @array to (1..100).to_a, and ran
through 50000 times.
Alex
On Tuesday 01 August 2006 17:06, A. S. Bradbury wrote: