8.2. Pointers to Structs

Any field referenced as a pointer is slightly more complex.

If the type is a parented struct or the field is possibly null, suffix the type with a question mark.

foo_t *myfoo;

public foo? myfoo;

The next question is: is the reference owned? If the value was overwritten, should the destructor be called? If the answer is no, then prefix with unowned. This is often the case for a tree structure that has parent pointers.

foo_t *parent;

public unowned Foo parent;

If unowned is missing, a double-free event will occur when the field is overwritten. If it is included when not needed, there will be a memory leak.