Iterator problem

spireup

Hi

I would like to use the iterator idea in ruby for my own classes but am struggling.

Heres an example thats not working


if Widget.each = 0 
  
  then puts "nuo"
  
  else
    for myWidget in Widget.each

      puts myWidget.xPos
  
    end
end

Any thoughts?

thanks

Paul

TIG

Paul

Your syntax seems to be shot to pieces...
What does 'Widget.each' generate ?? It needs a 'result' to work on like in the 'else' part!
An 'if test' uses '==' not '='... UNLESS you are testing to see if something that is set is then =0 and then it returns true ??
You don't need 'then' in your if's...
You seem to be mixing up 'if' and 'each' strangely... can you please explain in 'words' what you want to do and what each 'class/method' does... otherwise we are struggling

Chris Fullmer

if Widget.length == 0 
  
  puts "nuo"
  
  else
    Widget.each do |myWidget|

      puts myWidget.xPos
  
  end
end

I think this is what you're getting at, translated to ruby syntax, best as I can tell.

Jim

But what property of the Widget is to be iterated?

Very generically:


class Container
  def each
    if block_given?
      while(prop = next_property() != nil)
        yield(prop) # yield what?
      end
    end
  end
end
c = Container.new
c.each{|t| puts t}

But your class may use a built-in collection (like an Array) to store data internally, in which ase you can use the each method in your custom each method:


class Container
  include Enumerable
  def initialize
    @data_ = []
  end
  def each
    if block_given?
      @data_.each{ |d|  yield(d) }
    end
  end
end
c = Container.new
c.each{|t| puts t}

Once you define the each method, you can include Enumerable and get a bunch more iterators:

Enumerable.instance_methods ["find_all", "sort_by", "collect", "include?", "detect", "max", "sort", "partition", "any?", "to_a", "reject", "zip", "find", "min", "member?", "entries", "inject", "all?", "select", "each_with_index", "grep", "map"]

Dan Rathbun

Why not just define Widget to be a subclass of some standard class that has module Enumerable mixed-in?

class Widget < Array
  # define custom methods here
end # class

Widget will inherit an each iterator method from it's superclass, as well as an each_with_index method from Enumerable. (..and many other iterator methods, such as all, any, collect, etc.)

spireup

@tig said:

Paul

Your syntax seems to be shot to pieces...
You seem to be mixing up 'if' and 'each' strangely... can you please explain in 'words' what you want to do and what each 'class/method' does... otherwise we are struggling

Yes Im miles off!
What I want to do in words: I have a class called Widget. If there are no Widgets then I want to run a block of code. If there are some Widgets then I want to iterate through them and run a block of code using some or all of each Widgets properties.

TIG

What are these Widget 'properties' ?

spireup

@chris fullmer said:

I think this is what you're getting at, translated to ruby syntax, best as I can tell.

Hmmm. the .length didnt work. Came back undefined method. At the moment Widget is a bespoke class not like what the guys have suggested below.

spireup

@tig said:

What are these Widget 'properties' ?

Thanks TIG. Firstly my problem relates to all my classes rather than just one. Ive put Widget is as an example of my problem.

However most classes will have x,y,z position info as properties plus a bunch of meta info properties such as :windZone, :snowZone, :saltZone, :quakeZone.

Im mulling Dan and Jims suggestion of a subclass but Im not sure how these proeprties would fit into say a hash or an array. I read somewhere by ?thomthom that hashes perform better so Im going to try and work with them once I bend my head around them.

TIG

class Widget
  attr_accessor( ;x, ;y, ;z, ;length )###etc
  ### rest of methods
  ###
end

will return the instance variables @x, @length etc that will get set inside other class methods etc, in the form Widget.x or Widget.length etc......

Dan Rathbun

@spireup said:

I have a class called Widget. If there are no Widgets then I want to run a block of code. If there are some Widgets then I want to iterate through them and run a block of code using some or all of each Widgets properties.

You need two classes:

class WidgetSet < Array
end # class

MyWidgets = WidgetSet.new()

class Widget
  attr_accessor( ;x, ;y, ;z, ;length )###etc
  def initialize(*args)
    # args array can be used here to init
    # attribute values @x, @y, etc.
    MyWidgets < self # append this instance to set
  end
end #class

EDIT: you don't actually needs a custom Array subclass, you could do:
MyWidgets = []
and just use a normal Array if you don't need to add any custom methods to your Widget collection.

Dan Rathbun

BTW.. if you want your Widgets to persist across sessions.. perhaps Components and attached Attribute Dictionary might be a better solution. (You cannot add custom object class instances to a model's entities.)

spireup

@dan rathbun said:

BTW.. if you want your Widgets to persist across sessions.. perhaps Components and attached Attribute Dictionary might be a better solution. (You cannot add custom object class instances to a model's entities.)

Ok thats an important point. Yes I would like my widgets to persist. But Im wanting to do a lot of analytics on the components so maybe Im going to need to use attribute dictionaries for working within sketchup but hash based classes for doing the analytics.

I guess Im keen to learn each of the methods that has been suggested so I can choose the right one as I get more familiar with them and the project.

Could you show me some example code of your earlier suggestion but using Hash as a superclass. Im interested in seeing how the initialize method would look to have say 4 properties xPos, yPos, zPos , type?

spireup

@dan rathbun said:

You need two classes:

EDIT: you don't actually needs a custom Array subclass, you could do:
MyWidgets = []
and just use a normal Array if you don't need to add any custom methods to your Widget collection.

Yes youre right Dan Ive been reading about Containers at http://www.ruby-doc.org/docs/ProgrammingRuby/ and I see they use two classes Song and SongList in their example.

spireup

@tig said:

class Widget
>   attr_accessor( ;x, ;y, ;z, ;length )###etc
>   ### rest of methods
>   ###
> end

will return the instance variables @x, @length etc that will get set inside other class methods etc, in the form Widget.x or Widget.length etc......

Thanks TIG. Yes Ive figured out that attr_accessor and was successfully accessing my Classes properties but not in the context of the suggestions of using Arrays or Hashes as super classes.

Dan illustrates this

@dan rathbun said:

class WidgetSet < Array
> end # class
> 
> MyWidgets = WidgetSet.new()
> 
> class Widget
>   attr_accessor( ;x, ;y, ;z, ;length )###etc
>   def initialize(*args)
>     # args array can be used here to init
>     # attribute values @x, @y, etc.
>     MyWidgets < self # append this instance to set
>   end
> end #class

Now Im just trying to get the syntax right for those inner args arrays. eg(not working)

class WidgetSet < Array
end # class

class Widget < Hash
  
  attr_accessor ;arg1, ;xPos, ;yPos, ;zPos, ;height, ;width, ;type

  def initialize(arg1, xPos, yPos, zPos, height, width, type)
  
    Hash.new["arg1", arg1, "xPos",xPos,"yPos",yPos,"height", height, "width", width,"type", type] 
    @arg1 = arg1  ##etc for each arg
    MyWidgets < self 
  end

Dan Rathbun

@spireup said:

Now Im just trying to get the syntax right for those inner args arrays. eg(not working)

class WidgetSet < Array
> end # class
> 
> class Widget < Hash
>   
>   attr_accessor ;arg1, ;xPos, ;yPos, ;zPos, ;height, ;width, ;type
> 
>   def initialize(arg1, xPos, yPos, zPos, height, width, type)
>   
>     Hash.new["arg1", arg1, "xPos",xPos,"yPos",yPos,"height", height, "width", width,"type", type] 
>     @arg1 = arg1  ##etc for each arg
>     MyWidgets < self 
>   end

It does you no good to construct an object without a reference to it (the line with Hash.new).

If you want to use a Hash, then use one for your Widgets. They need not be a custom subclass, unless you need custom methods. Hashes dont need attributes (instance refs,) because they use key / value pairs, instead.

my_widget_1 = {
  'xPos' => 3.4,
  'yPos' => 1.0,
  'zPos' => 2.3,
  'height' => 6.784,
  'width' => 4.0,
  'type' => "some_type"
}

There is another thread on how to save and retrieve hashes into/from an Attribute dictionary.
see: http://forums.sketchucation.com/viewtopic.php?f=180&t=30066

Arguments: *list_name compacts an argument list into a local array referenced by list_name

Within the method, you can access array elements using the [] method.

def some_method(*args)
  @xPos =( args.size>0 ? args[0] ; 0.0 ) 
  @yPos =( args.size>1 ? args[1] ; 0.0 ) 
  # etc.  
end

If you use 5 arguments, but a call gives more than 5, the addtional arguments will be still be stored in the local array, and no ArgumentError, will be raised.

I suggest you visit the Code Snippet index:
http://forums.sketchucation.com/viewtopic.php?f=180&t=28846&p=323876#p322175