Using Objective-C achieve the stack structure.(用Objective-C实现堆栈)

Today I want to achieve the stack structure by using Objective-C Language.
First we need to define stack in a stack.h
As we can see in this file:
Stack.h:

#ifndef Using_Stack_Achieve_Queue_Stack_h#endif#define Using_Stack_Achieve_Queue_Stack_h#define ElementType inttypedef struct Node{//Initilize the Stack structure.    ElementType Data;//Data area.    struct Node *next;//Next point area.}LinkStack;//LinkStack *Top;//I need to pay attention to this error.Don't define a variate twice using same name in the same class(interface).@interface Stack_Node : NSObject{//Class for stack.    LinkStack *Top;//Initilize a Top point which server for finding item form the stack.    unsigned int size;//Record the size of the stack(item counter) as well as using as a flag to judge the stack whether is empty in Pop method.}-(LinkStack*)CreateStack;//Create a stack//-(int)isEmpty:(LinkStack*)S;//Cheack the stack S wheather it is Empty-(void)Push:(LinkStack*)S andItem:(ElementType)item;//Push the last element into the Stack-(ElementType)Pop:(LinkStack*)S;//Pop(Delect) the first element out of the Stack;-(void)print;//print the result in console.-(unsigned int)Size;//return the size of the stack.@end

As we can see that there are many methods we need to achieve just like:CreateStack、Push、Pop、print、Size.If you want to know some detail,you can see many explanation in my code and Stack.m.
So let we can see some details in Stack.m:
Stack.m

#import <Foundation/Foundation.h>#import "Stack.h"@implementation Stack_Node-(LinkStack*)CreateStack{//Create a new Stack.    LinkStack *S;    S = malloc(sizeof(LinkStack));//Open a momery for a new item.    S->next = NULL;//Make a empty stack.    size = 0;//item counter.    return S;}//-(int)isEmpty:(LinkStack*)S{//    return (S->next == NULL);//}-(void)Push:(LinkStack*)S andItem:(int)item{    LinkStack *TmpCell;    //create a new momery space for a temp item.    TmpCell = malloc(sizeof(LinkStack));    if (TmpCell == 0)    {        fprintf(stderr, "Out of memory\n");        return;    }    //If momery is full , printf error and break;    TmpCell->Data = item;//insert the item into the stack.    TmpCell->next = S->next;    S->next = TmpCell;    size++;//counter++;}-(ElementType)Pop:(LinkStack *)S{//Pop the first item    LinkStack *FirstCell;//deal with the firstitem.    ElementType TopElem;//    if (isEmpty(S)) {//        NSLog(@"堆栈空");//        return 0;//    }    if (size == 0) {//if the stack is empty.        return 0;    }    else{        FirstCell = S->next;        S->next = FirstCell->next;        TopElem = FirstCell->Data;        free(FirstCell);//free the momery.        size--;        return TopElem;    }}-(void)print{//print all items in console.    LinkStack *topLink;    topLink = Top;    while (topLink) {        NSLog(@"%4d",topLink->Data);        topLink = topLink->next;    }    NSLog(@"\n");}-(unsigned int)Size{    return size;}@end

So we can see the main frame for my project.We can see the main.m to show this:
main.m:

#import <Foundation/Foundation.h>#import "Stack.h"int main(int argc, char * argv[]){//    Stack_Node *S1,*S2;//    LinkStack *Stack1,*Stack2;//    for (int i = 0; i < 5; i++) {//        //    }    id stack;//get a new stack.    stack = [Stack_Node new];//initilize a interface for this stack.    [stack Push:(__bridge LinkStack *)(stack) andItem:10];    [stack Push:(__bridge LinkStack *)(stack) andItem:20];    [stack print];    [stack Push:(__bridge LinkStack *)(stack) andItem:5];    [stack Push:(__bridge LinkStack *)(stack) andItem:6];    [stack print];    [stack Pop:(__bridge LinkStack *)(stack)];    [stack print];    return 0;}程序的结果：