把一切东西都看成对象，一切用class来完成，更复杂的用design pattern来设计

本文发表在 rolia.net 枫下论坛针对接口编程能帮助达到面向对象开发和设计中"低耦合"的要求.
举个例子:某公司有一台特殊打印机,还可以使用一年,一年后可能换为另一种打印机,这两种打印机都特殊而贵.所以现在的程序希望换了打印机后也少量修改就可用.
方法:
1,定义一个打印机接口.
2,定义打印机类A,B,分别实现此接口.
3,定义一个工厂类,在类中可选择返回由A实现的接口,或者由B实现的接口.
4,在程序中使用打印机时,就可以使用工厂类来调用打印机,而不需要知道具体的是什么打印机.
如果打印机换了,只需要修改工厂类就行了.如果有一千个地方都调用过打印机,就不需要一个一个修改.修改一个地方就行了.接口充当一个隔离层的作用.

//定义打印机接口
interface Iprint{
bool PrintData(string data);
}

//定义打印机类A,实现接口
class PrintA:Iprint{
public virtual bool PrintData(string data){
//具体业务逻辑略
}
}

定义打印机类B,实现接口
class PrintB:Iprint{
public virtual bool PrintData(string data){
//具体业务逻辑略
}
}

//定义工厂类
class PrintFactory{
public Iprint CreatePrint(){
//返回一个由打机类A,或B实现的接口,比如
return new PrintA();
}
}

//通过工厂类,调用打印机
private void button1_Click(object sender,EventArgs e){
PrintFactory myFactory=new PrintFactory();
Iprint myPrint=myFactory.CreatePrint();
myPrint.PrintData("这样做很方便啊");
}更多精彩文章及讨论，请光临枫下论坛 rolia.net

本文发表在 rolia.net 枫下论坛Analysis
This section analyses the C++ code and its C translation and identifies the performance impact.

C++ Method Invocation All C++ methods when translated to C end up with an additional parameter. This might appear to be a big performance overhead. In reality however, the code in C will also have to access the common data structure via an array index or some other mechanism.

Object Construction Whenever an object is constructed, C++ will invoke the constructor. Sometimes this might be an addition overhead. This overhead can be reduced by defining the constructor inline. In most cases however, the constructor is actually replacing a routine that would have been used to initialize the data structures in a conventional C program.
If a program declares a lot of global objects, object construction can be a big overhead at program startup. C++ invokes constructors for all global objects before main() is called.


Object Destruction

As you can see from the C code, whenever an object goes out of scope or is explicitly deleted, C++ invokes the destructor for the object. This overhead can be reduced by only defining destructors when they are really needed (i.e. some action is required when object is deleted). Inline destructors can also be used to reduce the overhead.

Static Access The C code above shows that static member functions and variables do not correspond to an instance of the object. Thus they are accessed without indirection of the object. This can be useful in defining methods which need C level function call conventions. One good use for static member functions is to implement interrupt service routines (ISRs). ISRs handlers typically need to be C type functions. In most implementations, C++ static functions can be directly used as ISR handlers.更多精彩文章及讨论，请光临枫下论坛 rolia.net