对引用和指针使用以及函数返回引用和指针类型的理解.doc

引用的符号是&，指针的符号是*先来看看一段测试代码， 1: #include stdafx.h 2: #include 3: using namespace std; 4: int globalJ =999; 5: 6: /返回值 7: int test1() 8: 9: int j =1; 10: coutin test1(),return value the varaible js address :&jendl; 11: 12: return j; 13: 14: 15: /使用局部变量，返回引用 16: int& test2() 17: 18: int j =998; 19: coutin test2(),use field variable and return reference the local varaible Js address :&jendl; 20: coutin test2(),use field variable and return reference the local varaible Js value :jendl; 21: 22: return j; 23: 24: 25: /使用全局变量，返回引用 26: int& test3() 27: 28: 29: coutin test3(),use global variable and return reference the varaible globalJs address :&globalJendl; 30: 31: return globalJ; 32: 33: 34: 35: /返回指针 36: int* test4() 37: 38: int j =998; 39: coutin test4(),use field variable and return pointer the local varaible Js address :&jendl; 40: coutin test4(),use field variable and return pointer the local varaible Js value :jendl; 41: 42: 43: return &j; 44: 45: /返回指针 46: int* test5() 47: 48: coutin test5()use global variable and return pointer , the varaible globalJs address :&globalJendl; 49: return &globalJ; 50: 51: 52: 53: int main(int argc, char* argv) 54: 55: printf(Hello functions!n); 56: 57: int testresultvalue =0; 58: testresultvalue = test1(); 59: couttestResultValue address :&testresultvalue endl; 60: couttestResultValue value:testresultvalueendl; 61: coutslit line-endl; 62: 63: 64: int & testResultReference = test2(); 65: couttestResultReference address :&testResultReference endl; 66: couttestResultReference value:testResultReferenceendl; 67: coutslit line-endl; 68: 69: testResultReference = test3(); 70: couttestResultReference address :&testResultReference endl; 71: couttestResultReference value:testResultReferenceendl; 72: testResultReference = 4; 73: coutreset to 4endl; 74: couttestResultReference address :&testResultReference endl; 75: couttestResultReference value:testResultReferenceendl; 76: 77: coutslit line-endl; 78: 79: int & testResultReference2 = test3(); 80: couttestResultReference2 address :&testResultReference2 endl; 81: couttestResultReference2 value:testResultReference2endl; 82: coutslit line-endl; 83: 84: int* testResultPtr; 85: testResultPtr = test4(); 86: couttestResult address :testResultPtr endl; 87: couttestResult value:*testResultPtrendl; 88: coutslit line-endl; 89: 90: testResultPtr = test5(); 91: couttestResult address :testResultPtr endl; 92: couttestResult value:*testResultPtrendl; 93: coutslit line-temp; 99: 100: return 0; 101: 102: 然后我们来分析结果，test1 是返回值，没有什么好说的。test2本地变量的J的值是998，引用后得到的值是1245056. 因为在function作用域以外这块内存的东西就被释放掉了，所以值就不一致了。实际上，应该用全局变量（或类变量）。注意：J的内存地址和引用变量的地址是一样的。在编译中会报警告信息：warning C4172: returning address of local variable or temporarytest3globalJ全局变量的地址是00478DC0,但引用变量testresultreference的内存地址仍然是0012FF14。结论：引用变量一次赋值后即为只读，即使再次赋值，其引用对象不变。根据上面的情况我们新定义一个引用变量testresultre