iphone - 如果结构不适用于 NSDate 验证

Question

这是我检查两个NSDate对象是否具有值的代码，但问题是这个结构不起作用，我尝试将if语句更改为 example oldDate == nil，但这也不起作用。有什么想法吗？

    if (!oldDate && !newDate) {
        NSLog(@"oldDate & newDate are empty");
    }
    else {
        NSLog(@"oldDate & newDate have values");
    }

    if (!oldDate) {
        NSLog(@"oldDate is empty but newDate has a value");
    }
    else if (!newDate) {
        NSLog(@"newDate is empty but oldDate has a value");
    }

Answer 1

您有两个执行的 if/else 块。但你只想拥有一个：

if (!oldDate && !newDate) {
    NSLog(@"oldDate & newDate are empty");
} else if (!oldDate) {
    NSLog(@"oldDate is empty but newDate has a value");
} else if (!newDate) {
    NSLog(@"newDate is empty but oldDate has a value");
} else {
    NSLog(@"oldDate & newDate have values");
}