Why the NSString and string returned by JSON are not equal although both contain the same value

Question

When I assign the value to the bank: banca.name = @"CheBanca!"; the following condition returns true.

if(banca.name==@"CheBanca!"){
        header.bankNameLabel.textColor=[UIColor greenColor];
}

But when I assign the same value as: banca.name = [jsonBanca objectForKey:@"nome_banca"]; the condition return false although NSLog(@"Bank name: %@", [jsonBanca objectForKey:@"nome_banca"]); outputs the value Bank name: CheBanca!

The following code shows how I get jsonBanca:

NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
[responseData release];

NSDictionary *results = [responseString JSONValue];
[responseString release]; 

NSArray *jsonBanche = [results objectForKey:@"banche"];
NSLog(@"%@",jsonBanche);
NSMutableArray  *banks = [NSMutableArray arrayWithCapacity:jsonBanche.count];

for (int i=0; i<jsonBanche.count; ++i) {

        NSDictionary *jsonBanca = [jsonBanche objectAtIndex:i];
}

This code NSLog(@"%@",jsonBanche); returns the banks:

{
    "nome_banca" = "CheBanca!";
    "nome_prodotto" = "Conto Deposito";
    rating = "A-1";
}, ...

The question is why this two strings @"CheBanca!" and the string recieved by JSON are not equal although they contain the same phrase. And how to make them equal to return true in the condition.

possible duplicate of [If "a == b" is false when comparing two NSString objects?](http://stackoverflow.com/questions/8598599/if-a-b-is-false-when-comparing-two-nsstring-objects) — mmmmmm, Jan 03 '12 at 14:04

score 3 · Accepted Answer · edited Jan 03 '12 at 14:08

3

To compare strings accurately, you should use the isEqualToString method.

if ([banca.name isEqualToString:@"CheBanca!"]) {
   // strings match
   header.bankNameLabel.textColor=[UIColor greenColor];
}

edited Jan 03 '12 at 14:08

Manlio

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answered Jan 03 '12 at 14:03

Bill Burgess

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Guillaume · Answer 2 · 2012-01-03T14:10:28.177

2

To check for equality between two strings, use isEqualToString:

if ([banca.name isEqualToString:@"CheBanca!"]){
    header.bankNameLabel.textColor = [UIColor greenColor];
}

Your previous code (if (banca.name == @"CheBanca!") {) was only checking for equality of the pointer's address.

Get more details about the NSString class here.

edited Jan 03 '12 at 14:10

answered Jan 03 '12 at 14:03

Guillaume

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score 1 · Answer 3 · edited Jan 03 '12 at 14:07

1

The issue here is that NSString* is a pointer to a NSString, as they are loaded through separate ways they are two different NSStrings and have two different addresses. == compares the addresses and so sees them as different.

To compare the values of the string use the compare: and related methods of NSString or the isEqualToString: method

edited Jan 03 '12 at 14:07

Manlio

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answered Jan 03 '12 at 14:00

mmmmmm

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The use of compare: is overkill when just checking for equality. – Guillaume Jan 03 '12 at 14:04

Why the NSString and string returned by JSON are not equal although both contain the same value

3 Answers3