在OC中，如果自定義類，則要考慮賦值、持久化儲存、儲存到其它容器中等各種情況的物件複製和比較，下面是一個比較全面的自定義例子，在此僅作記錄：

自定義類：

KeyValuePairs.h：

#import <Foundation/Foundation.h>

@interface KeyValuePairs: NSObject <NSCopying>
@property (nonatomic,strong)NSString *identifier;
@property (nonatomic,strong)NSString *name;

@end

#import "KeyValuePairs.h"

@implementation KeyValuePairs

- (id)copyWithZone:(NSZone *)zone
{
    KeyValuePairs *kvp = [[[self class] allocWithZone:zone] init];
    kvp.identifier = self.identifier;
    kvp.name = self.name;
    return kvp;
}

- (BOOL)isEqualToKeyValuePairs:(KeyValuePairs *)kvp{
    if (!kvp) {
        return NO;
    }
    BOOL haveEqualName = (!self.name && !kvp.name) || [self.name isEqualToString:kvp.name];
    BOOL haveEqualIdentifier = (!self.identifier && !kvp.identifier) || [self.identifier isEqualToString:kvp.identifier];
    
    return haveEqualName && haveEqualIdentifier;
}

#pragma mark -NSObject
-(BOOL)isEqual:(id)object{
    if (self == object) {
        return YES;
    }
    if (![object isKindOfClass:[KeyValuePairs class]]) {
        return NO;
    }
    return [self isEqualToKeyValuePairs:(KeyValuePairs *)object];
}

- (NSUInteger)hash {
    return [self.name hash] ^ [self.identifier hash];
}

@end
 

    NSMutableDictionary *namesWillUpdateDic = [[NSMutableDictionary alloc] init];
    NSMutableArray *names = [[NSMutableArray alloc] init];
    for (int i = 0; i<1000; i++) {
        NSString *name = [NSString stringWithFormat:@"%d_zhangsan",i];
        NSString *identifier = [NSString stringWithFormat:@"%d_identifier",i];
        NSString *strObj = [NSString stringWithFormat:@"%d_strObj",i];
        KeyValuePairs *kvp = [[KeyValuePairs alloc] init];
        kvp.identifier = identifier;
        kvp.name = name;
        [namesWillUpdateDic setObject:strObj forKey:kvp];
        [names addObject:kvp];
    }
    
    for (int j = 0; j<1000; j++) {
        int index = arc4random()%1000;
        KeyValuePairs *kvp = [names objectAtIndex:index];
        NSString *strObj = [namesWillUpdateDic objectForKey:kvp];
        NSString *msg = [NSString stringWithFormat:@"index:%d,identifier:%@,email:%@,strObj:%@",index,kvp.identifier,kvp.name,strObj];
        NSLog(@"%@",msg);
    }
 

注意：

1、如果自定義類不實現NSCopying則無法進行持久化儲存（到檔案）、或錯誤賦值

2、如果自定義類不重寫isEqual則預設使用記憶體地址比較兩個物件，可能會出現意想不到的結果

3、isEqual和hash方法要同時重寫，否則isEqual方法判斷將不正確