我可以在 Swift 上將一個類傳遞給同一個類中的一個函數嗎（嘗試編寫一個使用 C++ 和 Swift 語言編寫的類）

Question

你好 Stack Overflow 的人們！ 這將是我第一次發帖，我對編程相對較新，去年年初才開始使用 C++，不久前我創建了一個程序來對 C++ 進行一些計算，我正在嘗試做與 Swift 相同的基本程序作為開始學習語言 (swift) 的一種方式，但 xcode 不斷給我關於我試圖訪問的數組中的變量的錯誤，基本上我試圖從類的數組中訪問變量 i我在類本身內部創建。 我真的不太擅長解釋，但我會向您展示我嘗試使用 swift 重新創建的 C++ 類：

class investors {
string name = " "; //Name of Investor
double investment = 0; // Amount Invested
double last_total = 0; // current total value of all investments(execluding this investment) just before adding the investment.
double percent = 0; // Percentage

public:

// Set and Get Functions for Values
void set_name(string new_name)             {name = new_name;}
void set_investment(double new_investment) {investment = new_investment;}
void set_last_total(double new_last_total) {last_total = new_last_total;}
void set_percent(double new_percent)       {percent = new_percent;}

string get_name()       {return name;}
double get_investment() {return investment;}
double get_last_total() {return last_total;}
double get_percent()    {return percent;}

void recalc_percent(vector <investors> &old_investors) { // Function that recalculates all previous percentage to account for the added investment
    for (int i = 0; i < old_investors.size(); i++) {
        double temp_percent = old_investors.at(i).get_percent();
        temp_percent = (temp_percent * last_total) / (last_total + investment);
        old_investors.at(i).set_percent(temp_percent);
    }
}

void calc_percent(vector <investors> &old_investors) { // Calculating Newly added percentage of investment added

    percent = (investment / (investment + last_total)) * 100;
    recalc_percent(old_investors);
}

double current_amount(double final_amount) { // Returns how much investor currently has in US Dollars
    return (percent * final_amount) / 100;
}

};

這就是我使用 swift 的地方：

class Investors{

var name: String
var investment = 0.0
var lastTotal = 0.0
var percent = 0.0

init(name: String, investment: Double, lastTotal: Double, percent: Double) {
    self.name = name
    self.investment = investment
    self.lastTotal = investment
    self.percent = percent
}

func recalc_percent(oldInvestors: [Investors]){

    for (people) in oldInvestors{
        var tempPercent = oldInvestors[people].percent // This is where my issue is.


    }


}

func calc_percent(oldInvestors: [Investors]){
    percent = (investment / (investment + lastTotal)) * 100 //I had an error over here as well.


}
}

swift 有什么限制？ 我認為這些限制意味着我必須以與 C++ 版本不同的方式編寫程序。

謝謝，我很抱歉這么粗魯地問這么簡單但又長的問題

編輯：swift 代碼中的第一個錯誤（我在發生錯誤的代碼旁邊進行了評論）給了我這樣的消息：無法使用類型為“投資者”的索引對“[投資者]”類型的值進行下標

稍后我將添加第二條錯誤消息。

Answer 1

您似乎沒有完全理解 swift 中的 for 循環是如何工作的。 在這樣的 for 循環中：

for (people) in oldInvestors{

}

這里的people會在每次迭代中包含對數組中每個元素的引用（指針）。 換句話說，這里的變量people其實和C++代碼中的old_investors.at(i)類似。

這就是使用people作為下標不起作用的原因。

我已經為您翻譯了其余的代碼：

class Investors{

    var name: String
    var investment = 0.0
    var lastTotal = 0.0
    var percent = 0.0

    init(name: String, investment: Double, lastTotal: Double, percent: Double) {
        self.name = name
        self.investment = investment
        self.lastTotal = investment
        self.percent = percent
    }

    func recalc_percent(oldInvestors: [Investors]){

        for investor in oldInvestors{
            var tempPercent = investor.percent
            investor.percent = (tempPercent * lastTotal) / (lastTotal + investment)

        }


    }

    func calc_percent(oldInvestors: [Investors]){
        percent = (investment / (investment + lastTotal)) * 100 

        recalc_percent(oldInvestors: oldInvestors)
    }

    func currentAmount(finalAmount: Double) -> Double {
        return (percent * finalAmount) / 100
    }
}

雖然你試圖做的事情很奇怪......

我建議您先閱讀 Apple 的Swift Guide上的所有內容，然后自己編寫一些Swift程序並在翻譯代碼之前進入Swift思維模式。