如何调用其它构造函数中构造？ [英] How call constructor inside other constructor?

问题描述

我的类有相当长的一段属性和我的构造函数中的一个集所有这些，我想默认的构造函数调用此另一个和使用属性集。但我需要先准备好参数，所以从头部不会帮助称之为

My class has quite some properties and one of my constructors sets them all, I want the default constructor to call this other one and use the set properties. But I need to prepare arguments first, so calling it from the header won't help.

下面是我想做什么：

public class Test
{
    private int result, other;

        // The other constructor can be called from header,
        // but then the argument cannot be prepared.
        public Test() : this(0)
        {
        // Prepare arguments.
        int calculations = 1;

        // Call constructor with argument.
        this(calculations);

        // Do some other stuff.
        other = 2;
    }

    public Test(int number)
    {
        // Assign inner variables.
        result = number;
    }
}

所以这是不可能的，没有人知道如何叫我的构造函数来设置里面的代码参数？目前，我存储从其他构造对象的副本，并复制所有的属性，它是真烦人。

So this is not possible, does anyone know how to call my constructor to set parameters inside code? Currently I'm storing a copy of the object from the other constructor and copying all the properties, it's really annoying.

推荐答案

是的。刚刚通过的第一个电话

Yes. just pass the value 1 in the first call

public class Test
{    
    private int result, other;
    public Test() : this(1)        
    {        
       // Do some other stuff.        
       other = 2;    
    }    
    public Test(int number)    
    {        
        // Assign inner variables.        
        result = number;    
    }

}

}

而你为什么不能做准备的说法？

And why can't you prepare the argument?

public class Test
{    
    private int result, other;
    public Test() : this(PrepareArgument())
    {        
       // Do some other stuff.        
       other = 2;    
    }    
    public Test(int number)    
    {        
        // Assign inner variables.        
        result = number;    
    }
    private int PrepareArgument()
    {
         int argument;
         // whatever you want to do to prepare the argument
         return argument;
    }
}

或...如果prepareArgument要被称为从默认的构造函数，那么就可以不依赖于任何参数传递。如果它是一个常量，只是让一个恒定的...

or... if the prepareArgument is to be called from the default constructor, then it cannot be dependent on any passed in arguments. If it is a constant, just make it a constant ...

public class Test
{   
    const int result = 1;
    private int result, other;
    public Test() 
    {        
       // Do some other stuff.        
       other = 2;    
    }    
}

，如果它的值是依赖于其它外部的状态，然后你可能会重新考虑你的设计...为什么调用构造函数首先之前不算呢？

if it's value is dependent on other external state, then you might rethink your design... Why not calculate it before calling the constructor in the first place?

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