Objective-C代码（array.indexOfObjectPassingTest）到Swift

问题描述：

如何在Swift中使用Objective-C代码，我试过，但是有些错误。

How can I use the Objective-C code below in Swift, I tried but something is wrong.

Objective-C： / p>

Objective-C:

NSUInteger index = [theArray indexOfObjectPassingTest:
            ^BOOL(NSDictionary *dict, NSUInteger idx, BOOL *stop)
            {
                return [[dict objectForKey:@"name"] isEqual:theValue];
            }
    ];

Swift（无效）：
$ b

Swift (Doesn't work):

let index = theArray.indexOfObjectPassingTest { (var dict: NSDictionary, var ind: Int, var bool: Bool) -> Bool in
                return dict.objectForKey("name")?.isEqual("theValue")
            }

答

我使用它并让它工作：

let theArray: NSArray = [["name": "theName"], ["name": "theStreet"], ["name": "theValue"]]

let index = theArray.indexOfObjectPassingTest { (dict, ind, bool) in return dict["name"] as? String == "theValue" }

if index == NSNotFound {
    print("not found")
} else {
    print(index)    // prints "2"
}

进一步减少。由于注释中提到的@newacct，因为闭包只有一行，所以可以删除 return 。此外， _ 可用于替换未使用的参数：

This can be further reduced. As @newacct mentioned in the comment, the return can be dropped since the closure is only a single line. Also, _ can be used in place of the parameters that aren't being used:

let index = theArray.indexOfObjectPassingTest { (dict, _, _) in dict["name"] as? String == "theValue" }

你可以完全摆脱闭包中的参数列表，默认的 $ 0 值。注意，在这种情况下，三个参数组合为一个元组，因此元组 dict 的第一个值被引用为 $ 0.0 ：

You can get rid of the parameter list in the closure entirely and use the default $0 value. Note in that case, the three parameters are combined as a tuple, so the first value of the tuple dict is referenced as $0.0:

let index = theArray.indexOfObjectPassingTest { $0.0["name"] as? String == "theValue" }

Objective-C代码（array.indexOfObjectPassingTest）到Swift

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