Collections之Pointer Collections

：指针集合类

    1. NSPointerArray
    1. NSHashTable
    1. NSMapTable

1.NSPointerFunctionsOptionsDefines the memory and personality options for an NSPointerFunctions object.

  • NSPointerFunctionsMachVirtualMemory

  • NSPointerFunctionsMallocMemory

       Use free() on removal, calloc() on copy in.

  • NSPointerFunctionsOpaqueMemory

  • NSPointerFunctionsStrongMemory

  • NSPointerFunctionsWeakMemory

      Uses weak read and write barriers appropriate for ARC or GC. Using NSPointerFunctionsWeakMemory object references will turn to NULL on last release.

  • NSMapTableStrongMemory

      Equivalent to  NSPointerFunctionsStrongMemory

  • NSMapTableWeakMemory

      Equivalent to NSPointerFunctionsWeakMemory.

2. NSPointerArray/NSHashTable/NSMapTable

  • 可以存储所有指针类型的数据包括nil
  • 可以添加或删除nil values
  • 可以弱引用或强引用对象。
  • 添加元素时，性能很差。慎用！！！