Question

我正在学习swift课程，我不得不为这个senario写一个代码，我不知道为什么我的功能不起作用。我非常恼火。

//: Playground - noun: a place where people can play

import Cocoa

// create class

class State
{
    var population: Double?
    var capital: String?
    var name: String?
    var growthRate: Double?
    var nextYearPopulation: Double?
    var neighbors: [State]


// initialize vars
    init(population: Double?, capital: String?, name: String?, growthRate: Double?, neighbors: [State])
    {
        self.population = population
        self.capital = capital
        self.name = name
        self.growthRate = growthRate
        self.neighbors = neighbors
    }

    var Texas = State(population: 1000000, capital: "Austin", name: "Texas", growthRate: 0.012, neighbors: [])

    var Oklahoma = State(population: 3000000, capital: "Oklahoma City", name: "Oklahoma", growthRate: 0.01, neighbors: [])

    var NewMexico = State(population: 1000000, capital: "Santa Fe", name: "New Mexico", growthRate: 0.02, neighbors: [])

    var NewYork = State(population: 25000000, capital: "New York City", name: "New York", growthRate: 0.1, neighbors: [])

    var Virginia = State(population: 15000000, capital: "Richmond", name: "Virginia", growthRate: 0.03, neighbors: [])

    var Florida = State(population: 20000000, capital: "Tallahassee", name: "Florida", growthRate: 0.07, neighbors: [])

    //functions

    func populationAfter()
    {
        nextYearPopulation = self.growthRate! * self.population!
        print("The projected population for ", self.name, "is ", nextYearPopulation)
    }

    Texas.populationAfter()


}

Answer 1

您需要移动州var并在课程定义后致电Texas.populationAfter()。 State具有Texas，Oklahoma等属性是没有意义的，但这就是您的代码所做的事情。在代码中调用Texas.populationAfter()是完全非法的，因为代码需要在函数声明中。

通过在State类之外创建状态，然后使用State类定义创建变量，然后可以在populationAfter()上调用State方法{1}}名为Texas的实例。

请注意，Swift建议使用以小写字母开头的字符串表示变量和属性，而字符串以类和结构类型的大写字母开头。

请注意，您的populationAfter功能只是计算人口增长。要获得新的更新人口，请乘以1 + self.growthRate!。

class State
{
    var population: Double?
    var capital: String?
    var name: String?
    var growthRate: Double?
    var nextYearPopulation: Double?
    var neighbors: [State]

    // initialize vars
    init(population: Double?, capital: String?, name: String?, growthRate: Double?, neighbors: [State])
    {
        self.population = population
        self.capital = capital
        self.name = name
        self.growthRate = growthRate
        self.neighbors = neighbors
    }

    //functions

    func populationAfter()
    {
        nextYearPopulation = (1 + self.growthRate!) * self.population!
        print("The projected population for ", self.name!, "is ", nextYearPopulation!)
    }
}

var Texas = State(population: 1000000, capital: "Austin", name: "Texas", growthRate: 0.012, neighbors: [])

var Oklahoma = State(population: 3000000, capital: "Oklahoma City", name: "Oklahoma", growthRate: 0.01, neighbors: [])

var NewMexico = State(population: 1000000, capital: "Santa Fe", name: "New Mexico", growthRate: 0.02, neighbors: [])

var NewYork = State(population: 25000000, capital: "New York City", name: "New York", growthRate: 0.1, neighbors: [])

var Virginia = State(population: 15000000, capital: "Richmond", name: "Virginia", growthRate: 0.03, neighbors: [])

var Florida = State(population: 20000000, capital: "Tallahassee", name: "Florida", growthRate: 0.07, neighbors: [])

Texas.populationAfter()

Swift类和函数

1 个答案: