判断字符串为空和只为空格(ios)

+ (BOOL)isBlankString:(NSString *)string{

if (string == nil) {

returnYES;

}

if (string == NULL) {

returnYES;

}

if ([string isKindOfClass:[NSNullclass]]) {

returnYES;

}

if ([[string stringByTrimmingCharactersInSet:[NSCharacterSetwhitespaceAndNewlineCharacterSet]] length]==0) {

returnYES;

}

returnNO;

}