c# - 工厂模式 C# 中缺少 return 语句

Question

我的代码有以下代码，但它总是说缺少 return 语句，即使我已将它们放入 switch 列表中。

public IMap Map(string oldtheme) 
{ 
    switch (oldtheme) 
    { 
        case "archer": return new Archer(); 
        case "craftyblue": return new CraftyBlue(); 
        case "minimal": return new Minimal(); 
        case "mintalicious": return new Mintalicious(); 
        case "misfit": return new Misfit(); 
        case "peach": return new Peach(); 
        case "queen": return new Queen(); 
        case "sketch": return new Sketch(); 
        case "takeaway": return new TakeAwayLemonFresh(); 
        case "lemonfresh": return new TakeAwayLemonFresh(); 
        case "vanilla": return new Vanilla(); 
        case "velvet": return new Velvet(); 
        case "victoriana": return new Victoriana(); 
        case "writer": return new Writer();
    }
}

Answer 1

您需要处理 oldtheme 不是您检查的值的情况。

根据您的情况，我建议抛出 ArgumentException这样您就知道它何时发生。我添加了default case 到您的 switch 语句:

public IMap Map(string oldtheme)
{
    switch ( oldtheme )
    {
        case "archer": return new Archer();
        case "craftyblue": return new CraftyBlue();
        case "minimal": return new Minimal();
        case "mintalicious": return new Mintalicious();
        case "misfit": return new Misfit();
        case "peach": return new Peach();
        case "queen": return new Queen();
        case "sketch": return new Sketch();
        case "takeaway": return new TakeAwayLemonFresh();
        case "lemonfresh": return new TakeAwayLemonFresh();
        case "vanilla": return new Vanilla();
        case "velvet": return new Velvet();
        case "victoriana": return new Victoriana();
        case "writer": return new Writer();
        default: throw new ArgumentException("unexpected value of oldtheme");
    }
}