iOS determines if the bank card number is valid

iOS determines if the bank card number is valid by Wusheying

+ (BOOL) Isvalidcreditnumber: (nsstring*) value {BOOL result = NO;    Nsinteger length = [value length];        if (length >=) {result = [Wtcreditcard isvalidnumber:value]; if (result) {Nsinteger twodigitbeginvalue = [[Value substringwithrange:nsmakerange (0, 2)] IntegerValue]            ; VISA if ([Wtcreditcard isstartwith:value str:@ "4"]) {if (= = length| |                = = length) {result = TRUE;                }else {result = NO; }}//mastercard else if (twodigitbeginvalue >= Wuyi && twodigitbeginvalue <=            (&& length = =) {result = TRUE; }//american Express else if (([Wtcreditcard isstartwith:value str:@ "34"]| | [Wtcreditcard isstartwith:value str:@ "37"])            && length = = () {result = TRUE; }//discover else if ([WTCREDITCARd Isstartwith:value str:@ "6011"] && length = = +) {result = TRUE;            }else {result = FALSE;            }} if (result) {Nsinteger digitvalue;            Nsinteger checkSum = 0;            Nsinteger index = 0;            Nsinteger Leftindex;                Even length, odd index if (0 = = length%2) {index = 0;            Leftindex = 1;                }//odd length, even index else {index = 1;            Leftindex = 0; } while (Index < length) {digitvalue = [[Value Substringwithrange:nsmakerange (index, 1)] int                Egervalue];                Digitvalue = digitvalue*2;                if (Digitvalue >=) {checkSum + = DIGITVALUE/10 + digitvalue%10;                } else {checkSum + = Digitvalue;           }     Digitvalue = [[Value Substringwithrange:nsmakerange (Leftindex, 1)] integervalue];                CheckSum + = Digitvalue;                Index + = 2;            Leftindex + = 2; } result = (0 = = checksum%10)?        True:false;    }}else {result = NO; } return result;

iOS determines if the bank card number is valid