CODEWITHSUNDEEP
objective-c
user979331
user979331

Reputation: 11961

Objective-c stringByAppendingString return string nil

I have this code here, basically it takes an array goes through each item and adds it to a string with a comma at the end and after the loop, remove the last comma:

NSString *areaDescriptionWSpaceCharacters = nil;

    for(NSString *item in areaDescription)
    {
        [areaDescriptionWSpaceCharacters stringByAppendingString:[NSString stringWithFormat: @"%@,", item]];
    }

    areaDescriptionWSpaceCharacters = [areaDescriptionWSpaceCharacters substringToIndex:[areaDescriptionWSpaceCharacters length] - 1];

but areaDescriptionWSpaceCharacters returns nil. Why?

Upvotes: 0

Views: 482

Answers (2)

Arun Gupta
Arun Gupta

Reputation: 2636

Your first line itself is the culprit here. You have not initialized the NSString yet so it will always be nil.

 NSString *areaDescriptionWSpaceCharacters;

or 

NSString *areaDescriptionWSpaceCharacters = @"";

or

NSString *areaDescriptionWSpaceCharacters = [[NSString alloc] init];

Upvotes: 1

Sulthan
Sulthan

Reputation: 130200

You are appending a string to nil. You need to initialize the string to an empty string first.

NSString *areaDescriptionWSpaceCharacters = @"";

In this case you might consider using NSMutableString.

NSMutableString *areaDescriptionWSpaceCharacters = [NSMutableString string];

for (NSString *item in areaDescription) {
    if (areaDescriptionWSpaceCharacters.length > 0) {
        [areaDescriptionWSpaceCharacters appendString:@","];
    }

    [areaDescriptionWSpaceCharacters appendString:item];
}

or directly

NSString *areaDescriptionWSpaceCharacters = [areaDescription componentsJoinedByString:@","];

(this task is so common there is a special method for it!)

Upvotes: 5

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