Swift stack and heap understanding

ios memory swift stack heap
Dániel Nagy picture Dániel Nagy · Dec 12, 2014 · Viewed 20.7k times · Source

I want to understand what is stored in the stack and heap in swift. I have a rough estimation: Everything that you print and the memory address appears not the values, those are stored in the stack, and what is printed out as values, those are on the heap, basically according to value and reference types. Am I completely wrong? And optionally, could you provide a visual representation of the stack/heap?

Answer

Jaydeep Vyas picture Jaydeep Vyas · Feb 25, 2017

As @Juul stated Reference types are stored in the Heap and values in the stack.

Here is the explanation:

Stack and Heap

Stack is used for static memory allocation and Heap for dynamic memory allocation, both stored in the computer's RAM .

Variables allocated on the stack are stored directly to the memory, and access to this memory is very fast, and its allocation is determined when the program is compiled. When a function or a method calls another function which in turns calls another function, etc., the execution of all those functions remains suspended until the very last function returns its value. The stack is always reserved in a LIFO order, the most recently reserved block is always the next block to be freed. This makes it really simple to keep track of the stack. Freeing a block from the stack is nothing more than adjusting one pointer.

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Variables allocated on the heap have their memory allocated at run time, and accessing this memory is a bit slower, but the heap size is only limited by the size of virtual memory. Elements of the heap have no dependencies with each other and can always be accessed randomly at any time. You can allocate a block at any time and free it at any time. This makes it more complex to keep track of which parts of the heap are allocated or free at any given time.

For Escaping Closure:
An important note to keep in mind is that in cases where a value stored on a stack is captured in a closure, that value will be copied to the heap so that it's still available by the time the closure is executed.

For more reference: http://net-informations.com/faq/net/stack-heap.htm

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