ios - Add whitespace after character in the TextField -

i creating sdk in user needs enter 4 digit pin , there should space after each character , textfield should securetextentry enabled .i writing following code

 - (bool)textfield:(uitextfield *)textfield shouldchangecharactersinrange:(nsrange)range replacementstring:(nsstring *)string {     nsuinteger newlength = [textfield.text length] + [string length] - range.length;      nsstring *text = [textfield.text stringbyreplacingcharactersinrange:range                                                              withstring: string];        if (text.length < 13)     {         textfield.text = [nsstring stringwithformat: @"%@  ", text];          return no;     }      return newlength <= 12;   } 

but problem adding space between character space shown dot . solution works fine in non sdk code . trying hard find easy solution

thanks in advance

    - (bool)textfield:(uitextfield *)textfield shouldchangecharactersinrange:(nsrange)range replacementstring:(nsstring *)string {           nsuinteger length = [textfield.text length] + [string length] - range.length;        if (length < 10) {      nsstring *newstring = [textfield.text stringbyreplacingcharactersinrange:range withstring:string];      nsstring *laststring = [nsstring stringwithformat:@"%c",[newstring characteratindex:newstring.length-1]];     if(![laststring isequaltostring:@" "] && ![string isequaltostring:@""])        newstring = [newstring stringbyappendingstring:@" "];    else {         nsrange tempr = nsmakerange(range.location-1, 2);         newstring = [textfield.text stringbyreplacingcharactersinrange:tempr withstring:@""];    }     textfield.text = newstring;   }  return no; 

}