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我做了这个简单的代码：

PO(self.last10000Places);
PO(PlaceMark);
NSMutableArray *placemarks= [NSMutableArray arrayWithArray:PlaceMark];
PO(placemarks);//Breakpoint1
[placemarks removeObjectsInArray:self.last10000Places];
PO(placemarks);//Breakpoint2
[self.last10000Places addObjectsFromArray:placemarks];

这里 PO 只是我的宏

#define CLog( s, ... ) NSLog( @"<%p %@:(%d)> %@", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __LINE__, [NSString stringWithFormat:(s), ##__VA_ARGS__] )
#define PO(x) CLog(@#x ": %@", x)
#define PD(x) CLog(@#x ": %f", x)

现在，我知道 nsmutablearray 需要实现 isEqual 。

所以我把这段代码：

@interface CLLocation  (equal)
- (BOOL)isEqual:(CLLocation*)other;
@end

@implementation CLLocation  (equal)

- (BOOL)isEqual:(CLLocation*)other {


    if ([self distanceFromLocation:other] ==0)
    {
        return true;
    }
    return false;
}
@end
@interface CLPlacemark (equal)
- (BOOL)isEqual:(CLPlacemark*)other;
@end

@implementation CLPlacemark (equal)

- (BOOL)isEqual:(CLPlacemark*)other {
    PO(self);
    PO(other);
    if (![self.name isEqual:other.name])
    {
        return false;
    }
    if (![self.location isEqual:other.location ])
    {
        return false; //NEVER called
    }
    return true;//breakpoint3 but strange result
}


@end

然后我单步执行代码。现在这很奇怪。

在断点1我看到：

2012-09-22 21:40:53.959 GetAllDistricts[18381:c07] <0x74a7480 SDViewController.m:(82)> placemarks: (
    "Ross Sea, Ross Sea @ <-77.43947520,-168.68218520> +/- 100.00m, region (identifier <-75.73637772,-0.00216940> radius 2140218.36) <-75.73637772,-0.00216940> radius 2140218.36m"

at breakpoint3 I saw:
2012-09-22 21:41:22.964 GetAllDistricts[18381:c07] <0xd77fab0 SDViewController.m:(37)> self: Alexander Island, Antarctica @ <-71.05224390,-70.87965290> +/- 100.00m, region (identifier <-70.73927686,-71.91489801> radius 258243.49) <-70.73927686,-71.91489801> radius 258243.49m
2012-09-22 21:41:22.964 GetAllDistricts[18381:c07] <0xd77fab0 SDViewController.m:(38)> other: South Atlantic Ocean, South Atlantic Ocean, Antarctica @ <-42.60533670,-21.93128480> +/- 100.00m, region (identifier <-41.51023865,-31.60774370> radius 4958095.65) <-41.51023865,-31.60774370> radius 4958095.65m
2012-09-22 21:41:22.965 GetAllDistricts[18381:c07] <0xd787390 SDViewController.m:(37)> self: South Atlantic Ocean, South Atlantic Ocean, Antarctica @ <-42.60533670,-21.93128480> +/- 100.00m, region (identifier <-41.51023865,-31.60774370> radius 4958095.65) <-41.51023865,-31.60774370> radius 4958095.65m
2012-09-22 21:41:22.965 GetAllDistricts[18381:c07] <0xd787390 SDViewController.m:(38)> other: South Atlantic Ocean, South Atlantic Ocean, Antarctica @ <-42.60533670,-21.93128480> +/- 100.00m, region (identifier <-41.51023865,-31.60774370> radius 4958095.65) <-41.51023865,-31.60774370> radius 4958095.65m

很明显，地标包含罗斯海。那么南大西洋到底removeObjectsinArray叫什么？isEqual

断点 2 也不会从地标中删除罗斯海。

我实现了 isEqual 我没有实现哈希

这是问题吗？

4

2 回答 2

2

我已经弄清楚了问题所在。实施 -(NSUInteger) 哈希以某种方式解决了这个问题。

文档说当我们覆盖 isEqual 时我们必须覆盖哈希

看起来 removeObjects 使用哈希进行优化并找出哈希不相等并得出结论 isEqual 将返回 false 而无需检查。

所以我只需添加以下代码：

@interface CLLocation  (equal)
- (BOOL)isEqual:(CLLocation*)other;
@end

@implementation CLLocation  (equal)

- (BOOL)isEqual:(CLLocation*)other {


    if ([self distanceFromLocation:other] ==0)
    {
        return true;
    }
    return false;
}

- (NSUInteger) hash
{
    NSUInteger theHash = (NSUInteger) (self.coordinate.latitude *360 + self.coordinate.longitude);
    CLog(@"thehash %d",theHash);
    return theHash;
}
@end
@interface CLPlacemark (equal)
- (BOOL)isEqual:(CLPlacemark*)other;
@end

@implementation CLPlacemark (equal)

- (BOOL)isEqual:(CLPlacemark*)other {
    PO(self);
    PO(other);
    if (![self.name isEqual:other.name])
    {
        return false;
    }
    if (![self.location isEqual:other.location ])
    {
        return false;
    }
    return true;
}

-(NSUInteger) hash
{
    return self.name.hash;
}
于 2012-09-22T18:28:55.517 回答
1

您的问题可能需要整理一下，也许是对当前行为的简明解释，以及它如何偏离预期。

但是，我想知道（根据您的问题的标题）您是否对该arrayWithArray:方法实际上创建并维护一个单独的集合这一事实感到困惑。您的对象不会被复制，但在这种情况下：

NSArray *objects = [NSArray arrayWithObjects:@"A", @"B", @"C", nil];
NSMutableArray *mute = [NSMutableArray arrayWithArray:objects];
NSArray *removals = [NSArray arrayWithObjects:@"A", @"C", nil];
[mute removeObjectsInArray:removals];

您的最终结果将是：

objects = { @"A", @"B", @"C" }
mute = { @"B" }

这个例子是否有助于澄清任何事情？

于 2012-09-22T16:00:32.247 回答