iphone - Change UILabel in loop -

i want change uilabel after 2 sec in loop. current code change last value after loop finished.

- (ibaction) start:(id)sender{      (int i=0; i<3; i++) {     nsstring *tempstr = [[nsstring alloc] initwithformat:@"%s", @" "];      int randomnumber = 1+ arc4random() %(3);      if (randomnumber == 1) {         tempstr = @"red";     }else if (randomnumber == 2) {         tempstr = @"blue";     } else {         tempstr = @"green";     }        nslog(@"log: %@ ", tempstr);        labelstext.text = tempstr;        [tempstr release];         sleep(2);      } } 

your code updates label last value function blocks main thread ui cannot updated. solve problem move updating code separate function , call using performselector:withobject:afterdelay: method. (or schedule calls using nstimer)

possible solution (you need handle case when user taps button several times in row, should not difficult):

- (ibaction) start:(id)sender{     [self updatelabel]; }  - (void) updatelabel{    static const nsstring* allstrings[] = {@"red", @"blue", @"green"};    static int count = 0;     int randomnumber = arc4random()%3;    nsstring *tempstr = allstrings[randomnumber];     nslog(@"log: %@ ", tempstr);    labelstext.text = tempstr;     ++count;    if (count)       [self performselector:@selector(updatelabel) withobject:nil afterdelay:2.0];  }