objective c - == and isEqualsToString giving strange behavior -

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• if “a == b” false when comparing 2 nsstring objects 5 answers

i have below code

nsstring *firstname = @"1.6.1"; nsstring *secondname = @"1.6.1";  if (!(firstname==secondname)) {     nslog(@"lock app"); } else {     nslog(@"do not lock app"); }  if (!([firstname isequaltostring:secondname])) {     nslog(@"lock app"); } else {     nslog(@"do not lock app"); } 

output getting

do not lock app not lock app 

however when use actual values firstname & secondname, output

lock app not lock app 

below details of firstname & secondname

 // coming server  firstname = [[nsuserdefaults standarduserdefaults] stringforkey:@"iphoneappversion"];   // coming app version iphone  secondname = [self appnameandversionnumberdisplaystring];  - (nsstring *)appnameandversionnumberdisplaystring {     nsdictionary *infodictionary = [[nsbundle mainbundle] infodictionary];     nsstring *appdisplayname = [infodictionary objectforkey:@"cfbundledisplayname"];     nsstring *majorversion = [infodictionary objectforkey:@"cfbundleshortversionstring"];     nsstring *minorversion = [infodictionary objectforkey:@"cfbundleversion"];      return [nsstring stringwithformat:@"%@",             minorversion]; } 

if print firstname & secondname, values 1.6.1, 1.6.1 respectively.

any idea why there 2 different outputs when using equals?

you different behaviour == , isequaltostring:. because == operator compares address of object , isequaltostring: compare string value.

you should not use == string comparison.