有没有一种简单的方法来编码ANSI C中的策略（或其他）设计模式，这将适合11“ MacBook Air？ [英] Is there a simple way to code the strategy (or other) design pattern in ANSI C that would fit on the screen of an 11" MacBook Air?

问题描述

似乎ANSI C中的OO不是今天对OO的青睐的方法。有没有人知道使用严格的ANSI C来编写一个简单的设计模式的方式，所以我可以向朋友证明这是可能的（Axel-Tobias Schreiners的书让我进行这个！）

It seems that OO in ANSI C is not the favored approach to OO today. Does anyone know of a way to code a simple design pattern using strict ANSI C so I can prove to a friend that it is possible?(Axel-Tobias Schreiners' book got me going on this!)

推荐答案

使用C的OO可以使用函数指针来实现，如在这个SO问题。

OO using C can indeed be implemented using function pointers as explained quite well in this SO question.

使用该帖子的信息，以下是我将如何使用基本继承在C中实现Strategy模式。

Using the info from that post, here's how I would implement a Strategy pattern in C using basic inheritance.

让我们使用以下C ++作为指导：

Lets use the following C++ as a guide:

class StrategyBase
{
    ...
    StrategyBase();
    virtual void strategyMethod() = 0;
    ...
};

class StrategyDerived
{
    ...
    StrategyDerived();
    void strategyMethod();
    ...
};

这里是相应的C代码：

typedef struct StrategyBase_t StrategyBase;
struct StrategyBase_t
{
    StrategyBase *base; /* must be first memeber */
    void (*strategyMethod)(const void *self);
};
StrategyBase *newStrategyBase();
void strategyMethod(const void *self);  /* the abstract method */

struct StrategyDerived
{
    StrategyBase *base; /* must be first memeber */
    void (*strategyMethod)(const void *self);
    /* more derived attributes here */
};
typedef struct StrategyDerived_t StrategyDerived;
StrategyDerived *newStrategyDerived();

这里是功能实现：

void strategyMethod(const void *self)
{
    /* If called with just a StrategyBase, strategyMethod will be NULL, *
     * so perhaps some sort of protection should be added here first    */
    ((StrategyBase*) self)->base->strategyMethod();
}

void strategyMethodDerived(const void *self)
{
    /* Put your implementation here */
}

/* StrategyBase constructor */
StrategyBase *newStrategyBase()
{
    StrategyBase *self = (StrategyBase*) malloc(sizeof(StrategyBase));
    self->base = self; /* See comment below about virtual table */
    self->strategyMethod = NULL; /* StrategyBase is abstract, right? */
    return self;
}

/* StrategyDerived constructor */
StrategyDerived *newStrategyDerived()
{
    StrategyDerived *self = (StrategyDerived*) malloc(sizeof(StrategyDerived));
    self->base = newStrategyBase();
    self->strategyMethod = self->base->strategyMethod = strategyMethodDerived;
    return self;
}

虚拟表实现非常基本，但应该工作理想情况下，应该实现更加健壮的东西。

The virtual table implementation is very basic, but should work. Ideally, something more robust should be implemented.

然后，您只需要在需要一个策略的Struct中使用一个指向StrategyBase的指针，并且您已经实现了一个策略模式在C.我没有尝试编译它，但这应该是一个好的起点。

Then you just have to use a pointer to StrategyBase in a Struct that needs a strategy, and there you have a strategy pattern implemented in C. I havent tried compiling it, but this should serve as a good starting point.

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