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创建自己的“int”或“string”类

inheritance int variables string .net

afollestad · 技术社区 · 16 年前

String和Int32类是不可继承的,我不知道这些继承接口中有什么允许类保存值。我想要的是这样的:

public class MyVariable : //inherits here
{
     //Code in here that allows it to get/set the value
} 

public static class Main(string[] args)
{
     MyVariable a = "This is my own custom variable!";
     MyVariable b = 2976;

     if(a == "Hello") { }
     if(b = 10) { }
     Console.WriteLine(a.ToString());
     Console.WriteLine(a.ToString());
}

4 回复 | 直到 16 年前

R. Martinho Fernandes 16 年前

你可以通过 overloading operators . 有一个关于 MSDN .

Either ):

public sealed class StringOrInt32
{
    private string stringValue;
    private int int32Value;
    private bool isString;

    public bool IsString { get { return isString; } }
    public bool IsInt32 { get { return !isString; } }

    public string StringValue
    {
        get
        {
            if(!isString) throw new InvalidOperationException();
            return stringValue;
        }
    }

    public int Int32Value
    {
        get
        {
            if(isString) throw new InvalidOperationException();
            return int32Value;
        }
    }

    public StringOrInt32(string value)
    {
        isString = true;
        stringValue = value;
    }

    public StringOrInt32(int value)
    {
        isString = false;
        int32Value = value;
    }

    // Allows writing this:
    // StringOrInt32 foo = "Hello world!";
    public static implicit operator StringOrInt32(string value)
    {
        return new MyVariable(value);
    }

    // Allows writing this:
    // StringOrInt32 foo = 42;
    public static implicit operator StringOrInt32(int value)
    {
        return new MyVariable(value);
    }

    // Allows writing this:
    // StringOrInt32 foo = "Hello world!;
    // string bar = (string)foo;
    // Though foo.StringValue directly would be better
    public static explicit operator string(StringOrInt32 value)
    {
        return value.StringValule;
    }

    // Allows writing this:
    // StringOrInt32 foo = 42;
    // int bar = (int)foo;
    // Though foo.Int32Value directly would be better
    public static explicit operator int(StringOrInt32 value)
    {
        return value.Int32Value;
    }

    public static bool operator==(StringOrInt32 left, StringOrInt32 right)
    {
        if(left.IsString != right.IsString)
            return false;
        if(left.IsString)
            return left.StringValue == right.StringValue;
        else
            return left.Int32Value == right.Int32Value;
    }

    public static bool operator!=(StringOrInt32 left, StringOrInt32 right)
    {
        return !(left == right)
    }

    // Don't forget to override object.Equals(), object.GetHashCode(),
    // and consider implementing IEquatable<StringOrInt32>
    // Also, null checks, etc
}

Dean Harding 16 年前

1234 "some string"

因此,为了支持所需的代码类型,您需要提供转换运算符,可以将int和string(以及其他任何类型)转换为您的类型。看一看这个 conversion operators MSDN中的主题。

Michael Shimmins 16 年前

如果您想在一个易于发送的包中存储不同类型的数据,例如字符串和int的组合,您可以按照上面的步骤进行:

public class MyVariable
{
    public string Name { get; set; }
    public int Age { get; set; }
}

然后:

MyVariable personOne = new MyVariable { Name = "John", Age = 34 };
MyVariable personTwo = new MyVariable { Name = "Joe", Age = 312 };

像IComparable和IFormattable这样的接口允许您以特定的方式使用新类型的实例,例如IComparable可以传递给排序列表,因为它能够将自己与另一个实例进行比较,并相应地对它们进行“排序”。

Samuel Neff 16 年前

最好的例子是 Nullable<T> . 这提供了所有值类型的可空版本,可以像内置的那样进行赋值:

int? x = 0;
int? y = null;

这样做的方式是 可为空<T> Nullable<int> 和代码 Nullable<int>.op_Implicit 透明地处理转换。

下面是一个完整的示例:

public struct MyVariable
{
    private int _intValue;
    private string _stringValue;

    public override bool Equals(object obj)
    {
        if (!(obj is MyVariable))
        {
            return false;
        }
        var y = (MyVariable) obj;
        return _stringValue == y._stringValue && _intValue == y._intValue;
    }

    public override int GetHashCode()
    {
        return (_stringValue ?? _intValue.ToString()).GetHashCode();
    }

    public override string ToString()
    {
        return _stringValue ?? _intValue.ToString();
    }

    public static implicit operator MyVariable(string value)
    {
        return new MyVariable { _stringValue = value };
    }

    public static implicit operator MyVariable(int value)
    {
        return new MyVariable { _intValue = value };
    }

    public static bool operator==(MyVariable variable, string value)
    {
        return variable._stringValue == value;
    }

    public static bool operator ==(MyVariable variable, int value)
    {
        return variable._intValue == value;
    }

    public static bool operator !=(MyVariable variable, string value)
    {
        return variable._stringValue == value;
    }

    public static bool operator !=(MyVariable variable, int value)
    {
        return variable._intValue == value;
    }

    public static void Test()
    {
        MyVariable a = "This is my own custom variable!";
        MyVariable b = 2976;

        if (a == "Hello") { }
        if (b == 10) { }
        Console.WriteLine(a.ToString());
        Console.WriteLine(a.ToString());
    }
}