如何找到数组中每个项目的字符数

Question

我正在写一个函数，该函数从字符数超过8的字典中打印字符串值。这是到目前为止的内容，但是我不确定如何公式化where条件，以便它查看字符数在数组中的每个字符串值中。

var stateCodes = ["NJ": "New Jersey", "CO": "Colorado", "WI": "Wisconsin", "OH": "Ohio"]

func printLongState (_ dictionary: [String: String]) -> (Array<Any>) {
let fullStateNames = Array(stateCodes.values)

for _ in fullStateNames where fullStateNames.count > 8 {
    print(fullStateNames)
    return fullStateNames
}

return fullStateNames
}

printLongState(stateCodes)

Answer 1

如果要使用for循环，则可以像这样进行操作。

func printLongState (_ dictionary: [String: String]) -> (Array<Any>) {
    var fullStateNames = [String]()
    for (_, value) in dictionary where value.characters.count > 8 {
        fullStateNames.append(value)
    }
    return fullStateNames
}

但这不是Swift中的Swifty方法，您可以做的是可以在您的Dictionary使用flatMap来创建string数组或使用dictionary.values.filter

在字典中使用flatMap

func printLongState (_ dictionary: [String: String]) -> (Array<Any>) {  
    return dictionary.flatMap { $1.characters.count > 8 ? $1 : nil }
}
// Call it like this way.
var stateCodes = ["NJ": "New Jersey", "CO": "Colorado", "WI": "Wisconsin", "OH": "Ohio"] 
print(printLongState(stateCodes)) //["Wisconsin", "New Jersey"]

在dictionary.values上使用过滤器

func printLongState (_ dictionary: [String: String]) -> (Array<Any>) {  
    return dictionary.values.filter { $0.characters.count > 8 }
}

Answer 2

只是filter您的结果，而不是使用for-loop ：

如果要返回字典，请使用以下命令：

func printLongState (_ dictionary: [String: String]) -> (Array<Any>) {
    let overEightChars = stateCodes.filter({ $0.value.characters.count > 8 })
    return overEightChars
}

如果要返回字符串数组，请使用以下命令：

func printLongState (_ dictionary: [String: String]) -> (Array<Any>) {
    return dictionary.values.filter { $0.characters.count > 8 }
}

Answer 3

尝试将filter与characters.count一起使用，如下所示：

var states = ["NJ": "New Jersey", "CO": "Colorado", "WI": "Wisconsin", "OH": "Ohio"]

states.filter({ (_, value) -> Bool in
    return value.characters.count > 8
}).map({ (_, value) in
    print(value)
})