Is data structure always automatically placed on the stack?

Data structures (struct) in iOS (Swift) are not always placed on the stack. Although structures are value types and are usually stored on the stack, in some cases they can be placed on the heap:

• If the structure is a local variable in a function, it is usually stored on the stack.
• If the structure is part of a class (which is a reference type), it is stored inside the object on the heap.
• If the structure is captured by a closure or used in a context where copying or storage outside the stack is required, it may be placed on the heap.

Thus, the placement of a structure depends on the context of use, and it is not always automatically on the stack.