Replacing nulls with empty string from JSON response not working in iOS

问题

I used below code to replace nulls from json response with empty string, but it is not working. Please help me out to fix this issue, i am getting nulls from server response in lot of scenarios and App crashes.

Code:

- (NSMutableDictionary *)recursive:(NSMutableDictionary *)dictionaryResponse {

    NSMutableDictionary *dictionary=[[NSMutableDictionary alloc]initWithDictionary:dictionaryResponse];
    for (NSString *key in [dictionary allKeys]) {
        id nullString = [dictionary objectForKey:key];
        if ([nullString isKindOfClass:[NSDictionary class]]) {
            [self recursive:(NSMutableDictionary*)nullString];
        }else if([nullString isKindOfClass:[NSArray class]]){
            for (int i=0; i<[nullString count]; i++) {
                id nullstr = [nullString objectAtIndex:i];

                if ([nullstr isKindOfClass:[NSDictionary class]]) {
                    [self recursive:(NSMutableDictionary*)nullstr];

                }

            }
        }else {
            if ((NSString*)nullString == (id)[NSNull null])
                [dictionary setValue:@"" forKey:key];
        }
    }
    return dictionary;
}

回答1:

try this:

- (NSMutableDictionary *)recursiveNullRemove:(NSMutableDictionary *)dictionaryResponse {

    NSMutableDictionary *dictionary = [dictionaryResponse mutableCopy];
    NSString *nullString = @"";
    for (NSString *key in [dictionary allKeys]) {
        id value = dictionary[key];

        if ([value isKindOfClass:[NSDictionary class]]) {

            dictionary[key] = [self recursiveNullRemove:(NSMutableDictionary*)value];  

        }else if([value isKindOfClass:[NSArray class]]){

            NSMutableArray *newArray = [value mutableCopy];
            for (int i = 0; i < [value count]; ++i) {

                id value2 = [value objectAtIndex:i];

                if ([value2 isKindOfClass:[NSDictionary class]]) {
                    newArray[i] = [self recursiveNullRemove:(NSMutableDictionary*)value2];                    
                }
                else if ([value2 isKindOfClass:[NSNull class]]){
                    newArray[i] = nullString;
                }
            }
            dictionary[key] = newArray;
        }else if ([value isKindOfClass:[NSNull class]]){
            dictionary[key] = nullString;
        }
    }
    return dictionary;
}

EDITED:

I hase find the problem in my answer, and now it fixed

this is check code:

NSDictionary *dict = @{@"1" : @{@"1.1": @"value", @"1.2" : [NSNull null]},
                       @"2" : @[@"2.1", @{@"2.2.1" : @"val", @"2.2.2" : [NSNull null]}],
                       @"3" : [NSNull null]};

dict = [self recursiveNullRemove:dict];

回答2:

here is simple method to remove the Null from the string

-(NSString *) removeNull:(NSString *) string
{
    NSRange range = [string rangeOfString:@"null"];
    if (range.length > 0 || string == nil) {
       string = @"";
    }
    string = [self trimString:string];
    return string;
}

-(NSString*) trimString:(NSString *)theString
{
    NSString *theStringTrimmed = [theString stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]];
    return theStringTrimmed;  
}

回答3:

if (![nullString isKindOfClass:[NSNull class]] ) 
 {
     return nullString;
 }
else
 {
     return @"";
 }

来源：https://stackoverflow.com/questions/26734271/replacing-nulls-with-empty-string-from-json-response-not-working-in-ios