如何找到數組中每個項目的字符數

Question

我正在寫一個函數，該函數從字符數超過8的字典中打印字符串值。這是到目前為止的內容，但是我不確定如何公式化where條件，以便它查看字符數在數組中的每個字符串值中。

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循環，則可以像這樣進行操作。

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

但這不是Swift中的Swifty方法，您可以做的是可以在您的Dictionary使用flatMap來創建string數組或使用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上使用過濾器

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

Answer 2

只是filter您的結果，而不是使用for-loop ：

如果要返回字典，請使用以下命令：

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

如果要返回字符串數組，請使用以下命令：

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

Answer 3

嘗試將filter與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)
})