用空字符串替換從服務器接收過來的NSNULL類型的數據

不少時候服務器傳過來的空數據是NSNULL類型的，客戶端沒有作好判斷，很容易形成程序崩潰。咱們能夠將傳過來的空數據用@""代替來解決問題。分別爲字典和數組添加一個類目方法，將接收的字典或數組調用該方法便可。代碼以下。

//字典
@interface NSDictionary (JRAdditions)
- (NSDictionary *)dictionaryByReplacingNullsWithStrings;
@end
@implementation NSDictionary (JRAdditions)
- (NSDictionary *)dictionaryByReplacingNullsWithStrings {
    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 dictionaryByReplacingNullsWithStrings] forKey:key];
        else if ([object isKindOfClass:[NSArray class]]) [replaced setObject:[object arrayByReplacingNullsWithBlanks] forKey:key];
    }
    return [NSDictionary dictionaryWithDictionary:[replaced copy]];
}
@end
//數組
@interface NSArray (NullReplacement)
- (NSDictionary *)arrayByReplacingNullsWithBlanks;
@end
@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 dictionaryByReplacingNullsWithStrings]];
        else if ([object isKindOfClass:[NSArray class]]) [replaced replaceObjectAtIndex:idx withObject:[object arrayByReplacingNullsWithBlanks]];
    }
    return [replaced copy];
}
@end