c++ anonymous union,struct -- 匿名联合体和机构体

c++ anonymous union,struct -- 匿名联合体和机构体

结构体和联合体各自的基本用法不赘述，仅说一下他们匿名时访问的情况。如果是token不同，可以直接跨层访问。例子

#include <iostream>
using namespace std;

struct zoo_obj{
        string name;
        union {
                unsigned int property;
                struct{  //plant
                        unsigned int
                                hasLeaf:1,
                                hasFlower:1,
                                hasTrunk:1,
                                hasRattan:1;
                };
                struct { //animal
                        unsigned int
                                isBackbone:1,
                                isOvipara:1,
                                hasLags:1,
                                hasWing:1;
                };
        };

};

int main(void)
{
        zoo_obj peony = {"peony",0};
        zoo_obj dog = {name:"dog",0};
        dog.hasLags = true;
        /* zoo_obj dog = {name:"dog",property:0};
         * sorry, unimplemented: non-trivial designated initializers
         * not supported
         */

        cout << peony.name << " hasLeaf " << peony.hasLeaf << endl;
        cout << dog.name << " hasLags " << dog.hasLags << endl;

}

输出

peony hasLeaf 0
dog hasLags 1

不支持像列子中name样的指定访问。如果指定了会报错

sorry, unimplemented: non-trivial designated initializers not supported