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comp.lang.ruby

Simple iteration in a function problem

Blake Miller

12/1/2006 6:57:00 PM

i'm trying to do this, and I'm stuck


class holderOfYs

def initialize()
@ys = Array.new
end

def addX( x )
@ys << x
end

# this is the problem function. all I want is the specific (ONE)
element
# from the @ys array that matches the id, but when you iterate over the
# array, i can't find a way to only have one element returned
def getXById(id)
@ys.each_with_index do |comp, index|
if( @ys[index].getUniqueId == id )
@ys.fetch(index)
end
end
end

class Y
@uniqueId

def getUniqueId
@uniqueId
end

end

class X < Y
def getUniqueId
super
end
end



I tried setting a variable like :
def getXById(id)
inst = X.new
@ys.each_with_index do |comp, index|
if( @ys[index].getUniqueId == id )
inst = @ys.fetch(index)
end
end

inst
end

...but I'm not looking to instantiate a new X, and even that solution
seems to screw up the @ys array.

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33 Answers

Joel VanderWerf

12/1/2006 7:09:00 PM

0

Blake Miller wrote:
...
> # this is the problem function. all I want is the specific (ONE)
> element
> # from the @ys array that matches the id, but when you iterate over the
> # array, i can't find a way to only have one element returned
> def getXById(id)

Instead of:

> @ys.each_with_index do |comp, index|
> if( @ys[index].getUniqueId == id )
> @ys.fetch(index)
> end
> end

try this:

@ys.find {|x| x.getUniqueId == id}

> end


--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Mike Fletcher

12/1/2006 7:10:00 PM

0

Blake Miller wrote:
> # this is the problem function. all I want is the specific (ONE)
> element
> # from the @ys array that matches the id, but when you iterate over the
> # array, i can't find a way to only have one element returned
> def getXById(id)
> @ys.each_with_index do |comp, index|
> if( @ys[index].getUniqueId == id )
> @ys.fetch(index)
> end
> end
> end

Perhaps

def getXById( id )
@ys.detect { |y| y.getUniqueId == id }
end

See the docs for Enumerable#detect about handling what's returned if
nothing is found.

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James Gray

12/1/2006 7:15:00 PM

0

On Dec 1, 2006, at 12:57 PM, Blake Miller wrote:

> i'm trying to do this, and I'm stuck

I've tried to answer your question and Rubyify your code a bit:

class YHolder
def initialize
@ys = Array.new
end

def add_y(y)
@ys << y
end
alias_method :<<, :add_y

def fetch_by_id(id)
@ys.find { |y| y.object_id == id }
end
alias_method :[], :fetch_by_id
end

class Y; end
class X < Y; end

holder, ids = YHolder.new, Array.new
10.times do
new_y_or_x = [Y, X][rand(2)].new

ids << new_y_or_x.object_id
holder << new_y_or_x
end

p holder # show the collection

# pick one by id
pick = ids[3]
p pick
p holder[pick]

# >> #<YHolder:0x1e2928 @ys=[#<Y:0x1e289c>, #<X:0x1e2874>, #<X:
0x1e284c>,
# >> #<Y:0x1e2824>, #<X:0x1e27fc>, #<Y:
0x1e27d4>,
# >> #<Y:0x1e27ac>, #<X:0x1e2784>, #<X:
0x1e275c>,
# >> #<Y:0x1e2734>]>
# >> 988178
# >> #<Y:0x1e2824>

__END__

Hope that helps.

James Edward Gray II

Blake Miller

12/1/2006 7:20:00 PM

0

Mike Fletcher wrote:
> Blake Miller wrote:
>> # this is the problem function. all I want is the specific (ONE)
>> element
>> # from the @ys array that matches the id, but when you iterate over the
>> # array, i can't find a way to only have one element returned
>> def getXById(id)
>> @ys.each_with_index do |comp, index|
>> if( @ys[index].getUniqueId == id )
>> @ys.fetch(index)
>> end
>> end
>> end
>
> Perhaps
>
> def getXById( id )
> @ys.detect { |y| y.getUniqueId == id }
> end
>
> See the docs for Enumerable#detect about handling what's returned if
> nothing is found.

I don't know where "detect" comes from (@ys is an array, and it doesn't
seem to be a method of Array)? however, I tried that and the result is
null, but I know for certain that the id being searched for does match
an element in the @ys array (because I wrote a function to print out the
ids in @ys)

--
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Blake Miller

12/1/2006 7:34:00 PM

0


>>
>> See the docs for Enumerable#detect about handling what's returned if
>> nothing is found.
>
> I don't know where "detect" comes from (@ys is an array, and it doesn't
> seem to be a method of Array)? however, I tried that and the result is
> null, but I know for certain that the id being searched for does match
> an element in the @ys array (because I wrote a function to print out the
> ids in @ys)

Sorry, missed that "Enumerable"

--
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Blake Miller

12/1/2006 7:36:00 PM

0


>
> # pick one by id
> pick = ids[3]
> p pick
> p holder[pick]
>
> # >> #<YHolder:0x1e2928 @ys=[#<Y:0x1e289c>, #<X:0x1e2874>, #<X:
> 0x1e284c>,
> # >> #<Y:0x1e2824>, #<X:0x1e27fc>, #<Y:
> 0x1e27d4>,
> # >> #<Y:0x1e27ac>, #<X:0x1e2784>, #<X:
> 0x1e275c>,
> # >> #<Y:0x1e2734>]>
> # >> 988178
> # >> #<Y:0x1e2824>
>
> __END__
>
> Hope that helps.
>
> James Edward Gray II

Note: The ids are strings. The @ys.find { |y| y.object_id == id } still
isn't working for me, i also tried y.object_id.equals(id) but I can't
seem to find the darn match : /

--
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Blake Miller

12/1/2006 7:40:00 PM

0


> I tried setting a variable like :
> def getXById(id)
> inst = X.new
> @ys.each_with_index do |comp, index|
> if( @ys[index].getUniqueId == id )
> inst = @ys.fetch(index)
> end
> end
>
> inst
> end
>
> ...but I'm not looking to instantiate a new X, and even that solution
> seems to screw up the @ys array.

I've also tried this:
def getXById(id)
matchingIndx = 0
@components.each_index do |index|
if( @components[index].getUniqueId == uniqueId )
matchingIndx = index
end
end

@components.fetch(matchingIndx)
end

but it just returns the 0th one every time (I'm assuming there wasn't a
match)

--
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Paul Lutus

12/1/2006 7:49:00 PM

0

Blake Miller wrote:

>
>>
>> # pick one by id
>> pick = ids[3]
>> p pick
>> p holder[pick]
>>
>> # >> #<YHolder:0x1e2928 @ys=[#<Y:0x1e289c>, #<X:0x1e2874>, #<X:
>> 0x1e284c>,
>> # >> #<Y:0x1e2824>, #<X:0x1e27fc>, #<Y:
>> 0x1e27d4>,
>> # >> #<Y:0x1e27ac>, #<X:0x1e2784>, #<X:
>> 0x1e275c>,
>> # >> #<Y:0x1e2734>]>
>> # >> 988178
>> # >> #<Y:0x1e2824>
>>
>> __END__
>>
>> Hope that helps.
>>
>> James Edward Gray II
>
> Note: The ids are strings. The @ys.find { |y| y.object_id == id } still
> isn't working for me, i also tried y.object_id.equals(id) but I can't
> seem to find the darn match : /

Please show us your code, and make it as simple as possible. Like this:

--------------------------------------

#!/usr/bin/ruby -w

b = "b"

b_id = b.object_id

ys = [ "a",b,"c","d" ]

puts ys.find { |i| i.object_id == b_id } # => "b"

puts ys.find { |i| i.object_id == b } # => nil

puts ys.find { |i| i.object_id == "b" } # => nil

--------------------------------------

Notice in your version of the code that "id" must equal the object id, not
the object.

--
Paul Lutus
http://www.ara...

Blake Miller

12/1/2006 8:04:00 PM

0

> Please show us your code, and make it as simple as possible. Like this:


class Widget

def initialize(title)
@components = Array.new
end

def add_component(component)
@components << component
end

def component(uniqueId) # note: uniqueId is a string
@components.find { |comp| comp.getUniqueId == uniqueId }
end
end

=========================================================
class SearchWidgetComponent
:attr_reader :uniqueId

def getUniqueId
@uniqueId
end
end

=============================
class SearchWidgetComparisonComponent

def getUniqueId
super
end
end


in my view index.rhtml, I have:
<% @sw.component("swComparisonComp1").some_func_call_on_swcc()... %>

I get an error " NoMethodError in Region#index" "You have a nil object
when you didn't expect it!" in index.rhtml at the
some_func_call_on_swcc() line

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Blake Miller

12/1/2006 8:08:00 PM

0

I think perhaps the problem is how I'm comparing strings. What is the
proper way to compare two strings, like:


@str1 = "boo"

def meth(str)
if( @str1 == str )
end

meth("boo")

Is that the appropriate way to compare them?

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