Sorting NSArray based on other Array with custom classes

Question

I desperately need to sort an array: heres the situation,

I need to rearrange / sort and replace arrays based on other an object class from another array.

ParentClass :NSObject{
  NSString *name;
  NSNumber *type;
}

This is the parent class, which fills up the parentArray

parentArray = { parentA, parentB, parentC }

This is another object class, it has ParentClass *parent.

@class ParentClass;

EntryClass: NSObject{
 NSString *name;
 NSNumber *number;
 ParentClass *parent;
}



Now I have an array entryArray = { entryX, entryY, entryZ };

entryX.parent is one of the ParentClasses and all of them are in parentArray.

entryX.parent  == ParentC;
entryY.parent  == ParentA;
entryZ.parent  == ParentB;

I want to sort this entryArray, according the sequence in parentArray. So if ParentArray is:

{
 ParentA,
 ParentB,
 ParentC
}

then I'd want the sorted entryArray to be

{
 entryY,
 entryZ,
 entryX
}

Also, if theres one entry Object is missing, entryZ, then the array should be

{
 entryY,
 @"0.0",
 entryX
}

If tried a number of ways but none really worked, any help is appreciated.

thanks

UPDATE: MORE CLARITy: suppose parentArray is in this sequence

{parentA, parentB}

, and entry array is in

{entryX, entryY}

, I want to rearrange entryArray and if

entryY.parent == parentA, and entryX.parent == parentB

, then based on their postions in parentArray, parentA being the first, i'd want entryY to be before entryX. result = {entryY, entryX}.

Community · Accepted Answer · 2017-05-23 12:23:59Z

6

In fact you have a "sort using selector method" (S.O. source):

- (NSComparisonResult)compareParents:(EntryClass*)otherObject {
    return [parentArray indexOfObject:self.parent] < [parentArray indexOfObject:otherEntry.parent];
}

NSArray *sortedArray;
sortedArray = [entryArray sortedArrayUsingSelector:@selector(compareParents:)];

Doing like this, when sorting entryArray, compareParents is used as a comparison method. That means that e1 will be "less than" e2 iff e1.parent is less than e2.parent. This is exactly what you want.

compareParents should be defines ad method of EntryClass and parentArray should be visible to it.

ORIGINAL ANSWER:

I am not sure I understand fully what you are trying to do; anyway, I would approach the problem using a dictionary where you associate each parent to its entry. That way, once you have your parent array sorted, you can iterate and find out which is the corresponding entry, which will also be (indirectly) sorted.

edited May 23, 2017 at 12:23

CommunityBot

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answered Feb 11, 2012 at 18:18

sergio

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11 Comments

jasonIM Over a year ago

Simply put I want to sort the entryArray based on the sequence of parent Objects in parentArray. Using dictionaries seems like the last resort, i was wondering if there could be a sortUsing selector kinda way..

jasonIM Over a year ago

Hey thanks for replying, but, how can I use the parentArray ? Since this sorting isn't happening within the parent's class, its happening in a view controller, and the sequence of entryArray would depend on the sequence of parent objects in ParentARRAY... Really appreciate your help!

sergio Over a year ago

Well, I was suggesting an NSDictionary because I could not see a direct relationship between an entry and its parent. This is definitely required if you want to sort entries based on their parents. I don't know if you could reconsider your design and having each entry point to its own parent, not (or in addition) to the full parent array.

jasonIM Over a year ago

hmm, the direct relation ship is that entryX.parent == parentB, entryY.parent == parentA. I'd like the entries to be sorted based on the Array that includes only the parents = {parent A, parentB}, in which case the result should be {entryX, entryY}. Your right, nsdict does seem like the only way out, but I'll be doing this in cellForRowAtIndex. and I've considered the design part, but this is kinda the only way i got..

sergio Over a year ago

if entryX.parent is exntryX's parent, and you want that entryX come before entryY whenever entryX's parent comes before entryY's parent, then the code I gave above will work. You need to sort the entries array in your view controller, not (or not only) the parents array. Can you view controller get a pointer to the entries array?

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