Why Does String Not Equal What Is Stored?

问题

This is a simple, odd question...

if(tableViewNum == @"One") {
        if ([drinkArray objectAtIndex:0] == currentDate) {
            [updatedArray addObject:drinkArray];
            NSLog(@"MADE THE ELSE1");
        }
        NSLog(@"MADE THE ELSE2");
    }
    else if (tableViewNum == @"Two") {
        if ([[drinkArray objectAtIndex:0] isEqualToString:yesterdayDate])
            [updatedArray addObject:drinkArray];
    } else {
        NSLog(@"MADE THE ELSE %@",tableViewNum);
        [updatedArray addObject:drinkArray];
    }

In the very first if statement I ask if tableViewNum == @"One"

But I don't go in that section of the if statement even though tableViewNum actually does equal @"One"

As you can see the very last NSLog all ways comes out as

MADE THE ELSE One

But if tableViewNum really equaled One it would have gone through the if statement not the else statement code...?????

回答1:

You can't compare strings with the == operator. Use isEqualToString instead:

if([tableViewNum isEqualToString:@"One"]) {
    // etc.

… and the same for the rest of the conditions. You're already doing it right in the second block.

回答2:

To be more specific, you shouldn't compare ANY objects using ==. This compares just the pointers. Use [obj isEqual: otherObj] or with NSStrings isEqualToString: as described above.

来源：https://stackoverflow.com/questions/11348809/why-does-string-not-equal-what-is-stored