ios 判断字符串是否为空

#define NULLString(string) ((![string isKindOfClass:[NSString class]])||[string isEqualToString:@""] || (string == nil) || [string isEqualToString:@""] || [string isKindOfClass:[NSNull class]]||[[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0)

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原文地址：https://www.cnblogs.com/liuting-1204/p/6645678.html