作为一个c#开发人员,我习惯了遍历构造函数:
class Test {
public Test() {
DoSomething();
}
public Test(int count) : this() {
DoSomethingWithCount(count);
}
public Test(int count, string name) : this(count) {
DoSomethingWithName(name);
}
}
在c++中有办法做到这一点吗?
我尝试调用类名和使用'this'关键字,但都失败了。
c++ 11:是的!
c++ 11及以后的版本也有同样的特性(称为委托构造函数)。
语法与c#略有不同:
class Foo {
public:
Foo(char x, int y) {}
Foo(int y) : Foo('a', y) {}
};
c++ 03:不
值得指出的是,你可以在你的构造函数中调用父类的构造函数,例如:
class A { /* ... */ };
class B : public A
{
B() : A()
{
// ...
}
};
但是,在c++ 03之前,你不能调用同一个类的另一个构造函数。
简单地说,你不能在c++ 11之前。
c++ 11引入了委托构造函数:
Delegating constructor
If the name of the class itself appears as class-or-identifier in the
member initializer list, then the list must consist of that one member
initializer only; such constructor is known as the delegating
constructor, and the constructor selected by the only member of the
initializer list is the target constructor
In this case, the target constructor is selected by overload
resolution and executed first, then the control returns to the
delegating constructor and its body is executed.
Delegating constructors cannot be recursive.
class Foo {
public:
Foo(char x, int y) {}
Foo(int y) : Foo('a', y) {} // Foo(int) delegates to Foo(char,int)
};
请注意,委托构造函数是一个全有或全无的提议;如果一个构造函数委托给另一个构造函数,则调用构造函数的初始化列表中不允许有任何其他成员。如果只初始化一次const/reference成员,这是有意义的。