C ++-成员变量聚合初始化

Question

In the following code:

class Class
{
private:
LUID luid;

public:
Class()
{
luid = { 0, 0}; // A. Does not compile
LUID test = {0, 0}; // B. Compiles
test = {1,1}; // C. Does not compile
}

Why are A and C not right, but B is fine?

The error I get for A and C is:

error C2059: syntax error : '{'

error C2143: syntax error : missing ';' before '{'

error C2143: syntax error : missing ';' before '}'

I think it has to do with the C++ version, although I am not sure which version this is using besides it not being very new.

Answer 1

Statement LUID test = {0, 0} is an initialization of a local variable using an initialization list; this is valid, as it is used in the course of a variable definition. test = {0, 0} , in contrast, is an assignment , as test is defined elsewhere. Assigning initializer lists is supported only in particular cases (eg when assigning to a scalar or to a particular sort of class type (cf., for example, braced-init-list assignment ).

Other cases, like, for example, arrays, cannot be assigned but just initialized:

typedef int LUID[2];

int main(){

    LUID t = { 10, 20 }; // compiles
    // t = { 10, 20};     // does not compile, since an array is not assignable

     return 0;
}