Function 将内联函数定义作为输入参数传递给函数

比如说，我有一个函数，它接受一个函数作为输入参数之一：

// modify passed string
func modifyString(paramString: String, modificationFunction: String -> String) -> String {
    return modificationFunction(paramString)
}

现在我可以定义这样一个函数：

func addLearningSuffix(inputString: String) -> String {
    var returnString = inputString + " is learning swift"
    return returnString
}

// adds suffix - is learning swift
modifyString("Miraaj",  addLearningSuffix) // returns "Miraaj is learning swift"

// adds prefix - Miraaj
modifyString("is learning swift",{
    (inputString: String) -> String in
    let result = "Miraaj " + inputString
    return result // returns "Miraaj is learning swift"
    })

modifyString(" is learning swift", func addSomeOtherPrefix(inputString: String) -> String{
    return "Miraaj" + inputString
})

然后像这样使用它：

func addLearningSuffix(inputString: String) -> String {
    var returnString = inputString + " is learning swift"
    return returnString
}

// adds suffix - is learning swift
modifyString("Miraaj",  addLearningSuffix) // returns "Miraaj is learning swift"

// adds prefix - Miraaj
modifyString("is learning swift",{
    (inputString: String) -> String in
    let result = "Miraaj " + inputString
    return result // returns "Miraaj is learning swift"
    })

modifyString(" is learning swift", func addSomeOtherPrefix(inputString: String) -> String{
    return "Miraaj" + inputString
})

在上面的例子中，我只是将函数名-addLearningSuffix作为输入参数传递给函数-modifyString，但是如果我想在同一行中定义函数，同时将其作为输入参数传递，该怎么办呢

我知道函数是闭包的特例，所以我可以像这样传递内联闭包：

func addLearningSuffix(inputString: String) -> String {
    var returnString = inputString + " is learning swift"
    return returnString
}

// adds suffix - is learning swift
modifyString("Miraaj",  addLearningSuffix) // returns "Miraaj is learning swift"

// adds prefix - Miraaj
modifyString("is learning swift",{
    (inputString: String) -> String in
    let result = "Miraaj " + inputString
    return result // returns "Miraaj is learning swift"
    })

modifyString(" is learning swift", func addSomeOtherPrefix(inputString: String) -> String{
    return "Miraaj" + inputString
})

或者像这样：

modifyString("is learning swift"){
    (inputString: String) -> String in
    let result = "Miraaj " + inputString
    return result
    }

但是为什么我不能像这样传递内联函数定义：

func addLearningSuffix(inputString: String) -> String {
    var returnString = inputString + " is learning swift"
    return returnString
}

// adds suffix - is learning swift
modifyString("Miraaj",  addLearningSuffix) // returns "Miraaj is learning swift"

// adds prefix - Miraaj
modifyString("is learning swift",{
    (inputString: String) -> String in
    let result = "Miraaj " + inputString
    return result // returns "Miraaj is learning swift"
    })

modifyString(" is learning swift", func addSomeOtherPrefix(inputString: String) -> String{
    return "Miraaj" + inputString
})

正在尝试哪个编译器抱怨：(

---

如果我做错了什么，请提出建议。

想想声明对象和使用对象之间的区别：

var a = 100
abs(a)

与直接使用它相比：

abs(100)

doThis( { x: String -> return x + " is talking" } )

声明和使用函数之间存在相同的区别：

func talk(x: String) { return x + " is talking" }
doThis(talk)

与直接使用它相比：

abs(100)

doThis( { x: String -> return x + " is talking" } )

书写

doThis( func talk(x: String) { return x + " is talking" } )

就像写作一样

abs(var a = 100)

---

这没有意义。

您可以，但要避免使用

func

关键字，也就是说，避免声明有趣的内容，但要使用闭包的匿名性质：

modifyString(" is learning swift", { inputString in "Miraaj" + inputString })

看