如何初始化内联结构类型的指针成员？

Question

With a type:

type A struct {
   B int, C *int
}

How do I initialise a pointer member to a non-zero value inline, without creating temporaries?

a := A{
    B: 42,
    C: ?,
}

Answer 1

For the specific example you've given you are limited in what you can do without introducing additional statements.

If you want C to point at an initialised integer variable, you will need an additional statement to define that variable since you can't take the address of an integer literal (i.e. &42 would be an error).

If you just want to initialise C as a pointer to a new zero value, you are in luck though and can set it to new(int).

If you were instead dealing with a different type that had an initialiser syntax, you would also been in luck. For example, if C was a pointer to a structure, you could initialise it to &TheStruct{...}.

If none of these are appropriate, and you are really only after code clarity for initialising *int variables, a helper function might fit your requirements. For example:

func makeIntPointer(v int) *int {
    return &v
}