How to compare objects using operator < or > in Objective-C?

Question

How do I compare two objects of a custom class in Objective-C? I try to overloading the

- (NSComparisonResult)compare:(id)other;

method. This works great if I call the method manually

if ([obj1 compare:obj2] == NSOrderedDescending) {  
    // do something  
}

Is there any way that I can do it like this?

if (obj1 > obj2) {
    // do something
}

Or is there another method that I need to overload?

What are you planning to do with the comparison? In case you want to insert individual items in a sorted order into a collection I recommend taking a look at `indexOfObject:inSortedRange:options:usingComparator:`. It is available for `NSArray` in Mac OS X v10.6 and later. — JJD, Apr 04 '11 at 16:12

score 8 · Accepted Answer · answered Apr 04 '11 at 14:38

8

This is not possible, since objective C doesn't have operator overloading. You are comparing pointer values.

answered Apr 04 '11 at 14:38

mvds

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Thank you for the statment. Now I can understand why comparing with > sometimes seems to work. Next time I will try not to compare pointer value. :) – user691219 Apr 06 '11 at 21:52

score 0 · Answer 2 · answered Apr 04 '11 at 18:18

One way to achieve this is for your class you can define comparisons to everything that make sense to compare with.

@interface MyClass : NSObject
{
    // your stuff
}
- (BOOL)isGreaterThanNumber:(NSNumber *)otherNumber;
+ (BOOL)compare:(MyClass *)myClass toNumber:(NSNumber *)otherNumber;

With well-named functions this isn't terribly different than overloading although yes it prevents you from using > and <. The actual code you write should be identical though as if overloading were included.

How to compare objects using operator < or > in Objective-C?

2 Answers2

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