Help with struct

[unclefester]

Hi, could someone please help me understand the following code:

struct TypeClass
{   TypeClass (Type t, const char **c) :: t(t), c(c) {}
};
 

Advanced thanks.

[weaknessforcats]

First, this code won't compile. The :: needs to be a single colon.

This is a struct TypeClass that has a constructor that takes Type t and a char** c as arguments. The code after which should be one colon is the initializer list and t(t) call constuctor on the Type class that takes a Type argument, that the copy constructor.

However, for that typo work, you need a TypeClass member of type Type named t. Otherwise, that ain't going rto compile.

Ditto for the c.

Remember, classes in C++ are implemented as struct. If you declare a struct and specify public/private/protected for each struct member, your struct is identical to a class.

The only difference betwen the struct and the class is that the default access for struct is public whereas for a class it is private. There are no other differences.

[unclefester]

First, this code won't compile. The :: needs to be a single colon.

This is a struct TypeClass that has a constructor that takes Type t and a char** c as arguments. The code after which should be one colon is the initializer list and t(t) call constuctor on the Type class that takes a Type argument, that the copy constructor.

However, for that typo work, you need a TypeClass member of type Type named t. Otherwise, that ain't going rto compile.

Ditto for the c.

Remember, classes in C++ are implemented as struct. If you declare a struct and specify public/private/protected for each struct member, your struct is identical to a class.

The only difference betwen the struct and the class is that the default access for struct is public whereas for a class it is private. There are no other differences.

Thanks so much weaknessforcats =) Could you clarify your explanation "The code after which should be one colon is the initializer list and t(t) call constuctor on the Type class that takes a Type argument, that the copy constructor."? I didn't quite get that. Thanks.

[weaknessforcats]

The initializization list for a class constrcutor follows a single colon placed after the right parenthesis. For example:

MyClass::MyClass(int arg) : mvar(arg) {}
 

Here the value of arg is used to initialize the member mvar when the member is created. This is how you pass constructor arguments to your member variables:

class MyClass
{
 
    Date dt;
 
    public:
      MyClass(int m, int d, int y);
};
MyClass::MyClass(int m, int d, int y) : dt(m,d,y) {}
 

The dt(m,d,y) calls Date::Date(int month, int day, int year).

Remember, C++ objects are initialized memberwise and you may need to call member variable constructors to get your object properly built.