如何检查数组是否为空?

I want to check if my array is empty or null, and on base of which I want to create a condition for example.

我想检查我的数组是否为空或空，在此基础上我想创建一个条件。

if(array ==  EMPTY){
//do something
}

I hope I'm clear what I am asking, just need to check if my array is empty?

我希望我讲得很清楚，只需要检查数组是否为空?

regards

问候

11 个解决方案

#1

100

if (!array || !array.count){
  ...
}

That checks if array is not nil, and if not - check if it is not empty.

它检查数组是否为nil，如果不是-检查它是否为空。

#2

if ([array count] == 0)

If the array is nil, it will be 0 as well, as nil maps to 0; therefore checking whether the array exists is unnecessary.

如果数组是nil，它也会是0，因为nil映射到0;因此，检查数组是否存在是不必要的。

Also, you shouldn't use array.count as some suggested. It may -work-, but it's not a property, and will drive anyone who reads your code nuts if they know the difference between a property and a method.

同样，不应该使用数组。算一些建议。它可以工作，但是它不是一个属性，如果任何读你的代码的人知道属性和方法之间的区别，他们会把你逼疯。

UPDATE: Yes, I'm aware that years later, count is now officially a property.

更新:是的，我知道数年后，count正式成为一项财产。

#3

you can try like this

你可以这样试试

if ([array count] == 0)

#4

Just to be really verbose :)

非常啰嗦:)

if (array == nil || array.count == 0)

#5

if (array == (id)[NSNull null] || [array count] == 0) {
    NSLog(@"array is empty");
}

#6

Since Apple added the new firstObject property to NSArray, this also works.

由于苹果将新的firstObject属性添加到NSArray中，这也起了作用。

if (array.firstObject == nil)
{
    // The array is empty
}

#7

As nil maps to 0, which equals NO, the most elegant way should be

因为nil映射到0，等于NO，最优雅的方式应该是

if (![array count])

the '==' operator is not necessary.

不需要'= '操作符。

#8

You can also do this kind of test using if (nrow>0). If your data object is not formally an array, it may work better.

您还可以使用if (nrow>0)进行这种测试。如果您的数据对象不是正式的数组，那么它可能工作得更好。

#9

null and empty are not the same things , i suggest you treat them in differently

空和空不是一回事，我建议你用不同的方式对待它们。

if (array == [NSNull null]) {
    NSLog(@"It's null");
} else if (array == nil || [array count] == 0) {
     NSLog(@"It's empty");
}

#10

Swift 3

斯威夫特3

As in latest version of swift 3 the ability to compare optionals with > and < is not avaliable

在最新版本的swift 3中，与>和 <比较选项的能力无法保证< p>

It is still possible to compare optionals with ==, so the best way to check if an optional array contains values is:

仍然可以将选项与==进行比较，因此检查可选数组是否包含值的最佳方法是:

if array?.isEmpty == false {
    print("There are objects!")
}

as per array count

按数组数

if array?.count ?? 0 > 0 {
    print("There are objects!")
}

There are other ways also and can be checked here link to the answer

还有其他的方法可以在这里找到答案的链接

#11

if (array == nil || array.count == 0 || [array isEqaul [NSNull Null]])

#1

100

if (!array || !array.count){
  ...
}