iOS - NSArray indexOfObject 不调用自定义的 isEqual

Question

我有一个重写 isEqual 方法的人员类:

#import "People.h"

@implementation People
@synthesize name = _name;


-(BOOL)isEqual:(id)object {
    NSLog(@"A.isEqual called");

    if ([object isKindOfClass:[NSString class]]) {
        NSString *name = object;
        return [self.name isEqualToString:name];
    }
    return [super isEqual:object];
}

@end

当我在数组中找到人时，它不会调用 isEqual 方法:

People* p1 = [People new];
        p1.name = @"A";

        People* p2 = [People new];
        p2.name = @"B";

        NSArray* peopleArray = [NSArray arrayWithObjects:p1, p2, nil];

        NSLog(@"find A %ld", [peopleArray indexOfObject:@"A"]);

        NSLog(@"isEqual A -> %@", [p1 isEqual:@"A"] ? @"Yes" : @"No");

这是输出:

2013-04-10 18:15:47.988 runone[6273:303] find A 9223372036854775807
2013-04-10 18:15:47.988 runone[6273:303] A.isEqual called
2013-04-10 18:15:47.989 runone[6273:303] isEqual A -> Yes

你知道这是为什么吗？

Answer 1

尽管 Apple 的文档 says isEqual: 被发送到数组中的每个对象，它以相反的方式执行 - 发送 isEqual: 到您正在搜索的对象。

由于假定 [a isEqual:b] == [b isEqual:a]，因此在大多数情况下它应该没有任何区别，但在您的情况下却有区别。

这是一个例子:

People* p1 = [People new];
p1.name = @"A";

People* p2 = [People new];
p2.name = @"B";

People* p3 = [People new];
p3.name = @"C";

NSArray* peopleArray = [NSArray arrayWithObjects:p1, p2, p3, nil];

NSLog(@"find A %ld", (unsigned long)[peopleArray indexOfObject:p3]);

在 People 的 isEqual 方法中:

-(BOOL)isEqual:(id)object
{
    NSLog(@"A.isEqual called %@", [self name]);
    ...
}

输出:

A.isEqual called C
A.isEqual called C
find A 2