+ (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;
}