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良好的設(shè)計(jì)應(yīng)該只暴露接口給用戶，所有的實(shí)現(xiàn)細(xì)節(jié)對(duì)用戶來說應(yīng)該是隱藏的，也就是說用戶只要給接口傳遞相應(yīng)的參數(shù)就行了，不需要管內(nèi)部是如何實(shí)現(xiàn)的，比如我們使用fopen，fseek，CreateWindow等函數(shù)會(huì)發(fā)現(xiàn)很好用，而不需要管fopen，fseek，CreateWindow函數(shù)內(nèi)部代碼是如何實(shí)現(xiàn)的，數(shù)據(jù)結(jié)構(gòu)是如何組織的，也就是說絕對(duì)不能暴露任何的細(xì)節(jié)給用戶，包括數(shù)據(jù)組織在內(nèi)。
--------------------------- interface1.h ---------------------------
#ifndef INTERFACE1_H #define INTERFACE1_H class DATA { private: int _i; short _j; public: DATA(); ~DATA(); void set(int i, short j); void get(int* i, short* j); }; #endif --------------------------- interface1.cpp --------------------------- #include "interface1.h" DATA::DATA() { _i = _j = 0; } DATA::~DATA() { _i = _j = 0; } void DATA::set(int i, short j) { _i = i; _j = j; } void DATA::get(int* i, short* j) { *i = _i; *j = _j; } --------------------------- test.cpp --------------------------- #include <stdio.h> #include "interface1.h" int main() { DATA data; int i; short j; data.set(2, 3); data.get(&i, &j); printf("i = %d, j = %d\n", i, j); return 0; }
--------------------------- interface.h ---------------------------
#ifndef INTERFACE_H #define INTERFACE_H void* data_create(); void data_set(void* dummy, int i, short j); void data_get(void* dummy, int* i, short * j); void data_destroy(void* dummy); #endif --------------------------- interface.c --------------------------- #include <stdlib.h> struct DATA { int i; short j; }; void* data_create() { return malloc(sizeof(struct DATA)); } void data_set(void* dummy, int i, short j) { struct DATA* data = dummy; data->i = i; data->j = j; } void data_get(void* dummy, int* i, short * j) { struct DATA* data = dummy; *i = data->i; *j = data->j; } void data_destroy(void* dummy) { free(dummy); } --------------------------- test.c --------------------------- #include <stdio.h> #include "interface.h" int main() { int i; short j; void* data = data_create(); data_set(data, 2, 3); data_get(data, &i, &j); printf("i = %d, j = %d\n", i, j); data_destroy(data); return 0; } 可以看的出來，C的實(shí)現(xiàn)只暴露了接口給用戶，內(nèi)部的實(shí)現(xiàn)細(xì)節(jié)都隱藏了起來，可是C++用類實(shí)現(xiàn)反而在頭文件暴露了實(shí)現(xiàn)細(xì)節(jié)。 當(dāng)然用C++也可以做到只暴露接口給用戶，不過實(shí)現(xiàn)起來會(huì)比較復(fù)雜，而且需要消耗更多的內(nèi)存（使用了虛函數(shù)）。
-------------------------------------- parent.h --------------------------------------
#ifndef PARENT_H #define PARENT_H class PARENT { public: virtual void set(int i, short j) = 0; virtual void get(int* i, short* j) = 0; }; PARENT* get_child(); #endif -------------------------------------- parent.cpp -------------------------------------- #include "parent.h" #include "child.h" PARENT* get_child() { return new CHILD; } -------------------------------------- child.h -------------------------------------- #ifndef CHILD_H #define CHILD_H #include "parent.h" class CHILD : public PARENT { private: int _i; short _j; public: CHILD(); ~CHILD(); void set(int i, short j); void get(int* i, short* j); }; #endif -------------------------------------- child.cpp -------------------------------------- #include "child.h" CHILD::CHILD() { _i = _j = 0; } CHILD::~CHILD() { _i = _j = 0; } void CHILD::set(int i, short j) { _i = i; _j = j; } void CHILD::get(int* i, short* j) { *i = _i; *j = _j; } -------------------------------------- test.cpp -------------------------------------- #include <stdio.h> #include "parent.h" int main() { int i; short j; PARENT* parent = get_child(); parent->set(2, 3); parent->get(&i, &j); printf("i = %d, j = %d\n", i, j); return 0; } |
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