import "NSArray+Demo.h"

import <objc/message.h>

@implementation NSArray (Demo)

• (void)load{
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
  @autoreleasepool {
  [self exchangeMethodWithClass:objc_getClass("__NSArray0") orginSelector:@selector(objectAtIndex:) customSelector:@selector(emptyObjectIndex:)];
  [self exchangeMethodWithClass:objc_getClass("__NSSingleObjectArrayI") orginSelector:@selector(objectAtIndex:) customSelector:@selector(singleArrObjectIndex:)];
  [self exchangeMethodWithClass:objc_getClass("__NSArrayI") orginSelector:@selector(objectAtIndex:) customSelector:@selector(arrObjectIndex:)];
  [self exchangeMethodWithClass:objc_getClass("__NSArrayM") orginSelector:@selector(objectAtIndex:) customSelector:@selector(mutableObjectIndex:)];
  [self exchangeMethodWithClass:objc_getClass("__NSArrayM") orginSelector:@selector(insertObject:atIndex:) customSelector:@selector(mutableInsertObject:atIndex:)];
  }
  });
  }

• (void)exchangeMethodWithClass:(Class)class orginSelector:(SEL)orginS customSelector:(SEL)customS{
  Method orginMethod = class_getInstanceMethod(class, orginS);
  Method customMethod = class_getInstanceMethod(class, customS);
  method_exchangeImplementations(orginMethod, customMethod);
  }

• (id)emptyObjectIndex:(NSInteger)index{
  return nil;
  }

• (id)singleArrObjectIndex:(NSInteger)index{
  @autoreleasepool {
  if (index >= self.count || index < 0) {
  return nil;
  }
  return [self singleArrObjectIndex:index];
  }
  }

• (id)arrObjectIndex:(NSInteger)index{
  @autoreleasepool {
  if (index >= self.count || index < 0) {
  return nil;
  }
  return [self arrObjectIndex:index];
  }
  }

• (id)mutableObjectIndex:(NSInteger)index{
  @autoreleasepool {
  if (index >= self.count || index < 0) {
  return nil;
  }
  return [self mutableObjectIndex:index];
  }
  }

• (void)mutableInsertObject:(id)object atIndex:(NSUInteger)index{
  @autoreleasepool {
  if (object) {
  [self mutableInsertObject:object atIndex:index];
  }
  }
  }

• (id)myObjectAtIndex:(NSUInteger)index{
  @autoreleasepool {
  if (index < self.count) {
  return [self myObjectAtIndex:index];
  } else {
  return nil;
  }
  }
  }