How to efficiently loop through multiple nested NSDictionaries and compare values? - objective-c

Question

I have the following structure in an NSDictionary that I got after parsing the XMl using XMl reader from here http://troybrant.net/blog/2010/09/simple-xml-to-nsdictionary-converter/:
{
Document = {
Page = (
{
TextLR = {
Line = {
LineProps = {
applyBreakingRules = true;
autoDecimalTabPos = 0;
breakJust = BreakOptimal;
direction = ES;
hyphenationZone = 0;
kindAlign = Left;
kindJust = FullInterWord;
left = 0;
presSuppressWiggle = true;
rightBreak = 0;
rightJustify = 0;
text = "\n\t\n\t\t\n\t\t\t\n\t\t\t\t";
treatHyphenAsRegular = true;
};
Text = {
text = "\n\t\t\t\tHello ";
};
betweenBottom = false;
betweenTop = false;
bottomEnable = false;
break = EndPara;
cpLim = 12;
cpStart = 0;
direction = ES;
doc = Main;
firstLineCp = true;
};
bottom = 114115;
cpLim = 12;
cpStart = 0;
doc = Main;
left = 0;
right = 2438349;
text = "\n\t\t";
top = 0;
};
cpLim = 81963072;
fBuggyJust = false;
fEmptyPage = false;
fHasBubbles = false;
fSlicedPage = false;
height = 3448422;
marginBottom = 3448422;
},
{
TextLR = {
Line = {
LineProps = {
applyBreakingRules = true;
autoDecimalTabPos = 0;
breakJust = BreakOptimal;
direction = ES;
hyphenationZone = 0;
kindAlign = Left;
kindJust = FullInterWord;
left = 0;
presSuppressWiggle = true;
rightBreak = 0;
rightJustify = 0;
text = "\n\t\n\t\t\n\t\t\t\n\t\t\t\t";
treatHyphenAsRegular = true;
};
Text = {
text = "\n\t\t\t\tHello SO ";
};
betweenBottom = false;
betweenTop = false;
bottomEnable = false;
break = EndPara;
cpLim = 12;
cpStart = 0;
direction = ES;
doc = Main;
firstLineCp = true;
};
bottom = 114115;
cpLim = 12;
cpStart = 0;
doc = Main;
left = 0;
right = 2438349;
text = "\n\t\t";
top = 0;
};
cpLim = 81963072;
fBuggyJust = false;
fEmptyPage = false;
fHasBubbles = false;
fSlicedPage = false;
height = 3448422;
marginBottom = 3448422;
}
);
doc = "simple1.htm";
xdpi = 72;
xmlns = "http://apple/sites;
"xmlns:xsi" = "http://www.w3.org/2001/XMLSchema-instance";
"xsi:schemaLocation" = "xmlns = "http://apple/sites/Dump.xsd";
ydpi = 72;
};
}
I have been struggling to iterate through this nested NSDictionary and extract each attribute to compare with another NSDictionary of similar structure. The dictionaries can be somewhat dynamic, as in there might be additional levels of nesting for different xml files but the dictionaries to compare are of exact similar structure with same tags. Is there a way to iterate and create nested dictionaries on the go and then have parallel loops going so that I can extract the values and compare with between 2 NSDictionaries? I have tried the following code, but I am stuck in finding a good way to make it create dictionaries dynamically at the same time compare values/attributes with another dictionary. Help is much appreciated.
NSArray *arrPages = [[_xmlDictionary_master objectForKey:#"Document"] objectForKey:#"Page"];//this would return the array of Page dictionaries
for(int i=0;i<[arrPages count];i++){
NSDictionary *aPage = [arrStation objectAtIndex:i];
NSLog(#"id = %#",[aStation objectForKey:#"id"]);
}
Above code returns 2 Nested key/value pairs which in turn have multiple nested dictionaries. I am finding it hard to know which value has nesting and which doesnt during run time.

Answer 1

First tip: Refactor your data so that this isn't such a difficult operation! If that's not possible there's a few things you can try.
Rather than a "for loop", use:
[arrStation enumerateObjectsWithOptions: NSEnumerationConcurrent
usingBlock: ^(NSDictionary *aPage, NSUInteger idx, BOOL *stop) {
// Code here for compare
}];
That may perform your operations in parallel.
Another technique is using GCD. Using a dispatch_async, then a dispatch_apply can achieve something very similar.
dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
dispatch_apply([arrStation count], dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(size_t idx) {
// Work here
});
});
Spend some time reading through the Concurrency Programming Guide. It's a great way to understand what options are available and how they work.