Fix Duplicate Query Results: Use NSOrderedSet instead of NSArray

[sapieneptus]

Motivation

Suppose you have a hierarchy:

myView <UIView>
    └ myScrollView <UIScrollView>
        └ myLabel <UILabel>

And you do a query

query "* UILabel"

You will end up returning 3 duplicate copies of myLabel.

Explanation

"* UILabel" means any UILabel, or any descendent of a UIView that is a UILabel. myLabel matches this condition on three separate occasions:

1. myLabel is a UILabel that has descended from myView, which is a UIView
2. myLabel is a UILabel that has descended from myScrollView, which is a UIView
3. myLabel is a UILabel

Walkthrough

# Evaluation algorithm for finding views by class
def find(view, class):
    res = []
    if view.matches(class):
        res.add(view)
    for subview in view.subviews:
        res.addAll(find(subview, class))

# query string: "* UILabel" =>  "UIView UILabel" 
# So we are searching for all UIViews, then from those results, 
# we check if any result is a UILabel, recurse on the subviews, 
# and return cumulation of all UILabel results. 

find(mainWindow, UIView) =>  [ myView, myScrollView, myLabel ]  #returns the whole heirarchy 

#Then we recurse on each match, but searching for UILabel
find(myView, UILabel) => [ myLabel ]
find(myScrollView, UILabel) => [ myLabel ]
find(myLabel, UILabel) => [ myLabel ]

#Final return value:
[ myLabel, myLabel, myLabel ]

This can be easily resolved if we use an NSMutableOrderedSet to gather results instead of an NSMutableArray.

[jmoody]

Won't using NSSet loose the order?

[sapieneptus]

NSOrderedSet