objective-c - 替换 NSDictionary 中的所有 NSNull 对象

Question

我很好奇，由于 json-framework 的帮助，我目前有一个 NSDictionary，其中一些值被设置为 NSNull 对象。

目的是去除所有 NSNull 值并用空字符串替换它。

我确定有人在某处这样做过？毫无疑问，它可能是一个四线，而且很简单，我实在是太累了，无法自己解决这个问题。

Answer 1

我对 Jacob 的原始答案进行了一些更改，以将其扩展为处理存储在原始字典中的字典和数组。

#import "NSDictionary+NullReplacement.h"
#import "NSArray+NullReplacement.h"

@implementation NSDictionary (NullReplacement)

- (NSDictionary *)dictionaryByReplacingNullsWithBlanks {
    const NSMutableDictionary *replaced = [self mutableCopy];
    const id nul = [NSNull null];
    const NSString *blank = @"";
    
    for (NSString *key in self) {
        id object = [self objectForKey:key];
        if (object == nul) [replaced setObject:blank forKey:key];
        else if ([object isKindOfClass:[NSDictionary class]]) [replaced setObject:[object dictionaryByReplacingNullsWithBlanks] forKey:key];
        else if ([object isKindOfClass:[NSArray class]]) [replaced setObject:[object arrayByReplacingNullsWithBlanks] forKey:key];
    }
    return [NSDictionary dictionaryWithDictionary:[replaced copy]];
}

@end

当然还有一个数组类别:

#import "NSArray+NullReplacement.h"
#import "NSDictionary+NullReplacement.h"

@implementation NSArray (NullReplacement)

- (NSArray *)arrayByReplacingNullsWithBlanks  {
    NSMutableArray *replaced = [self mutableCopy];
    const id nul = [NSNull null];
    const NSString *blank = @"";
    for (int idx = 0; idx < [replaced count]; idx++) {
        id object = [replaced objectAtIndex:idx];
        if (object == nul) [replaced replaceObjectAtIndex:idx withObject:blank];
        else if ([object isKindOfClass:[NSDictionary class]]) [replaced replaceObjectAtIndex:idx withObject:[object dictionaryByReplacingNullsWithBlanks]];
        else if ([object isKindOfClass:[NSArray class]]) [replaced replaceObjectAtIndex:idx withObject:[object arrayByReplacingNullsWithBlanks]];
    }
    return [replaced copy];
}

@end

有了这个，您可以使用任何数组或字典并递归地清除所有 [NSNull null] 实例。

附言为了完成起见，这里是头文件:

@interface NSDictionary (NullReplacement)

- (NSDictionary *)dictionaryByReplacingNullsWithBlanks;

@end

和数组头:

@interface NSArray (NullReplacement)

- (NSArray *)arrayByReplacingNullsWithBlanks;

@end