如何通过其类的成员(即int或float)对NSMutableArray对象进行排序 [英] How to sort an NSMutableArray of objects by a member of its class, that is an int or float

问题描述

我有一个来自NSObject的类，其中包含:

I have a class (from NSObject) that contains:

NSString name
int      position
float    speed

然后我从该类创建对象的数组(NSMutableArray).然后，我想按'speed'值对数组进行排序，该值是float.

I then create an array (NSMutableArray) of objects from this class. I would like to then sort the array by the 'speed' value, which is a float.

最初，我将float值作为NSNumber，将int值作为NSInteger，并且我成功地使用了:

I initially has the float value as an NSNumber and the int as NSInteger, and I was successfully sorting with:

[myMutableArray sortUsingFunction:compareSelector context:@selector(position)];

其中myMutableArray是我的对象数组.

这是函数:

static int compareSelector(id p1, id p2, void *context) {
    SEL methodSelector = (SEL)context;
    id value1 = [p1 performSelector:methodSelector];
    id value2 = [p2 performSelector:methodSelector];
    return [value1 compare:value2];
}

现在我使用的是int而不是NSInteger，上面的代码不起作用.我应该使用更底层的命令来执行排序吗?谢谢！

Now that I am using int instead of NSInteger, the above code does not work. Is there a more low-level command that I should be using to execute the sort? Thank!

推荐答案

类似于drawonward，我建议在您的课程中添加一个比较方法:

Similar to drawnonward, I'd suggest adding a comparison method to your class:

- (NSComparisonResult)compareSpeed:(id)otherObject
{
    if ([self speed] > [otherObject speed]) {
        return NSOrderedDescending;
    } else if ([self speed] < [otherObject speed]) {
        return NSOrderedAscending;
    } else {
        return NSOrderedSame;
    }
}

(您可以使用三元运算符test ? trueValue : falseValue折叠if-else if-else，或者如果speed是具有compare:方法的对象(例如NSNumber)，则可以只是return [[self speed] compare:[otherObject speed]];.)

(You could collapse the if-else if-else using the ternary operator: test ? trueValue : falseValue, or if speed is an object with a compare: method (such as NSNumber), you could just return [[self speed] compare:[otherObject speed]];.)

然后您可以排序

[myMutableArray sortUsingSelector:@selector(compareSpeed:)];

正如Georg在评论中建议的那样，您也可以使用NSSortDescriptor实现目标；如果您的目标是10.6，则还可以使用块和

As suggested by Georg in a comment, you can also achieve your goal using NSSortDescriptor; if you're targeting 10.6, you can also use blocks and sortUsingComparator:(NSComparator)cmptr.

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