Copy: pass by value. Reserve a new space in memory. Value will not change if the original item's value changed.
Strong: pass by reference. Point to the same space in menory. Value will change as the same with the original item's value changed.
Copy: pass by value. Strong: pass by reference
Copy: pass by value. Reserve a new space in memory. Value will not change if the original item's value changed.
Strong: pass by reference. Point to the same space in menory. Value will change as the same with the original item's value changed.
Copy: pass by value. Strong: pass by reference