Can I overload an operator in Objective-C?

Is it possible to override operator use i开发者_运维知识库n Objective-C?

For example

myClassInstance + myClassInstance

calls a custom function to add the two.

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Operator overloading is not a feature of Objective-C. If two instances of your classes can be added together, provide a method and allow them to be added using that method:

Thing *result = [thingOne thingByAddingThing:thingTwo];

Or, if your class is mutable:

[thingOne addThing:thingTwo];

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No, you can't do this in Objective-C.

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You can do this now in Swift, a successor to objC. And since Objective-C and Swift are made to work together This could be interesting for you.

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You may want to support subscripting for your object. Subscripting is not operator overloading, but it can be handy for a collection object. NSArray and NSDictionary both support subscripting. For example:

NSMutableArray *a = [NSMutableArray new]; a[0] = @"Hello";

The way to support index subscripting is to implement the following:

-(id)objectAtIndexedSubscript:(NSUInteger)idx; -(void)setObject:(id)newObject atIndexedSubscript:(NSUInteger)idx];

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I know this is an old question but I just wanted to leave this answer here for anybody in the future that might want to know if this is a possibility.

The answer is YES!

You'll have to use a variant of Objective-C called Objective-C++. As an example, say you created a new Objective-C command-line tool project. In order to allow C++ functionality, you'll need to rename "main.m" to "main.mm". Afterwards, you can mix C++ code in with your Objective-C code in the same file. There are some limitations, but I've tested operator overloading and it seems to work perfectly fine with Objective-C objects as far as I can tell. I've included sample source code to give you an idea of how to do it:

//main.mm
#import <Foundation/Foundation.h>
#include <iostream>
#include <string>

std::ostream &operator<<(std::ostream &os, NSString *s) {
    os << [s UTF8String];
    return os;
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {

        NSString *str = @"I'm an NSString!";
        std::cout << str << std::endl;

    }
    return 0;
}

Here's my output after building and running this code:

I'm an NSString!
Program ended with exit code: 0

Hopefully this will be of help to somebody!

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No, Objective-C does not support operator overloading.

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First, operator overloading is evil. Second, C doesn't have operator overloading, and Objective-C is a proper superset of C, which only adds a handful of keywords and a messaging syntax.

That being said, if you're using Apple's development environment, you can use Objective-C++ instead of Objective-C, which gives you access to all of C++'s mistakes and misfeatures, including operator overloading. The simplest way to use Objective-C++ is just to change the extension on your implementation files from ".m" to ".mm"