Question

是否有一种有效的方法可以在不使用嵌套for循环的情况下从AllData获取包含“names”字符串的Array？我得到的代码是：“Alice”，“Brad Smith MD”，“Quam博士”，“Jennifer Johnson”，“John Banks MD”作为输出，但我想在没有嵌套for循环的情况下这样做，因为它不是很有效O n ^ 2而且难以阅读？我在Xcode 8.2中使用Swift 3

 var AllData:Array<Dictionary<String,String>> = []

 override func viewDidLoad() {
         super.viewDidLoad()

    AllData = [["pic":"Alice.png","name":"Alice Smith","position":"Nurse"],
               ["pic":"brad.png","name":"Brad Smith MD","position":"Primary Doctor"],
               ["pic":"user.png","name":"Dr. Quam","position":"Immunologist"],
               ["pic":"jennifer.jpg","name":"Jennifer Johnson","position":"Case Manager"],
               ["pic":"user.png","name":"John Banks MD","position":"Cardiologist"]
               ]

let names = ""

for thing in AllData { //thing is pic, name, position

                    for (key, value) in thing {
                        if(key == "name"){
                            names.append(value)
                            //print(value)
                        }
                    }
                }

 print(names)
}

Answer 1

绝对没有理由在字典中迭代一组(key, value)对，比较键直到找到特定匹配，只使用该值。只需直接下标字典：

var names = ""
for dict in AllData { //thing is pic, name, position
    guard let name = dict["name"] else { continue }
    names.append(name)
}
print(names)

功能方法更快更简单：

let names = AllData.flatMap{ $0["name"] }.joined(separator: "")

此外，您不应使用Dictionary来存储具有静态密钥集的数据。如果使用结构或类来封装数据，那么您将拥有更简单，更快速且更安全的代码。最终结果看起来像这样：

struct Employee {
    let pic: String
    let name: String
    let position: Sting //TODO: would this be better as an enum?
}


class MyVC: UIViewController {
    //...

    let employees = [
        Employee(
            pic: "Alice.png",
            name: "Alice Smith",
            position: "Nurse"
        ),
        Employee(
            pic: "brad.png",
            name: "Brad Smith MD",
            position: "Primary Doctor"
        ),
        Employee(
            pic: "user.png",
            name: "Dr. Quam",
            position: "Immunologist"
        ),
        Employee(
            pic: "jennifer.jpg",
            name: "Jennifer Johnson",
            position: "Case Manager"
        ),
        Employee(
            pic: "user.png",
            name: "John Banks MD",
            position: "Cardiologist"
        )
    ]

    override func viewDidLoad() {
        super.viewDidLoad()

        let names = employees.map{ $0.name }.joined(separator: "")

        print(names)
    }

    //...
}

dict和struct方法都是O(employees.count)，但结构方法的开销较低，样板代码较少，并且可以让您轻松处理非String员工数据。

提取字符串数组的有效方法来自数组<dictionary <string，string>＆gt;

1 个答案: