Is there a way to call a member function in init list?

Is there a way to call a function in init list with no context of data memeber?

For example this:

class x{
public:
    x(char ch): ..., foo() {} // doesn't work
...
    void foo(); //foo sets the keys in keys[], different keys for different ch
private:
    char keys[10];
}

instead of this:

class x{
public:
    x(): ...  {foo();}
...
    void foo(); 
private:
    char keys[10];
}

Does the init list syntax always have to be {data member name}(value)?

Also, I read that it's preferable to use init list instead of the constructor's function because this way it doesn't make a copy, but in this case does it matter?