IOS ID The last one is X, enter 17 digits after auto-complete X

Non-original, reproduced from http://blog.csdn.net/l2i2j2/article/details/51542028
If the last digit of the ID is x, enter 17 digits and auto-complete X

//TextField Proxy Method-(BOOL) TextField: (Uitextfield *) TextField Shouldchangecharactersinrange: (nsrange) range replacementstring: ( NSString *)string {    //String.Length is 0, indicating that there are no input characters, should be being deleted and should return yes.     if(string. length = =0) {        returnYES; }    //length is the characters in the current input boxNsuinteger length = TextField.text.length +string. Length; //If there are other input boxes in the page, you need to make this decision    if(TextField = =Self.idnumbertextfield) {//Str is the character in the current input boxNSString *str = [NSString stringWithFormat:@"%@%@", Textfield.text,string]; //when input to 17 digits, the last one is judged by the Thelastisx method is x        if(Length = = -&&[self thelastisx:str]) {            //if it is 17 bits, and the first 17 bits are calculated 18 bits x, Auto-complete, and return no, prohibit editing. Textfield.text = [NSString stringWithFormat:@"%@%@x", Textfield.text,string]; returnNO; }        //returns less than or equal to 18 (up to 18 bits) if other conditions are true        returnLength <= -; }    returnYES;}//Judging if the last one is X-(BOOL) THELASTISX: (NSString *) IDNumber {Nsmutablearray*idarray =[Nsmutablearray array];  for(inti =0; I < -; i++) {Nsrange range= Nsmakerange (I,1); NSString*substring =[IDNumber Substringwithrange:range];    [IDArray addobject:substring]; } Nsarray*coefficientarray = [Nsarray arraywithobjects:@"7",@"9",@"Ten",@"5",@"8",@"4",@"2",@"1",@"6",@"3",@"7",@"9",@"Ten",@"5",@"8",@"4",@"2", nil]; intsum =0;  for(inti =0; I < -; i++) {        intcoefficient =[Coefficientarray[i] intvalue]; intID =[Idarray[i] intvalue]; Sum+ = coefficient *ID; }    if(Sum% One==2)returnYES; Else returnNO;}

IOS ID The last one is X, enter 17 digits after auto-complete x (Turn)