1、对于非容器对象（NSString）
不可变 （NSString）
copy ：浅复制，指针指向
mutableCopy：深复制，生成可变字符串对象
可变（NSMutableString）
copy： 深复制，生成不可变字符串对象
mutableCopy ：深复制，生成可变字符串对象
2、对于容器类对象 数组
不可变（NSArray）
copy ：浅复制，指针指向
mutableCopy：深复制，生成可变数组对象（但，数组中的对象没有进行处理的话，数组的中的对象是浅复制）
可变（NSMutableArray）
copy ：深复制，生成不可变数组对象
mutableCopy：深复制，生成不可变数组对象
test:
NSString *str1 = @"123"; NSLog(@"%p",str1); NSString *str2 = [str1 copy]; NSLog(@"%p",str2); NSMutableString *str3 = [str1 mutableCopy]; NSLog(@"%p",str3); NSMutableString *str4 = [[NSMutableString alloc]initWithString:@"123"]; NSLog(@"%p",str4); NSString *str5 = [str4 copy]; NSLog(@"%p",str5); NSMutableString *str6 = [str4 mutableCopy]; NSLog(@"%p",str6); NSArray *array1 = [[NSArray alloc] initWithObjects:@3,@4, nil]; NSLog(@"%p",array1); NSArray *array2 = [array1 copy]; NSLog(@"%p",array2); NSMutableArray *array3 = [array1 mutableCopy]; NSLog(@"%p",array3); NSMutableArray *array4 = [[NSMutableArray alloc]initWithObjects:@2,@3, nil]; NSLog(@"%p",array4); NSArray *array5 = [array4 copy]; NSLog(@"%p",array5); NSMutableArray *array6 = [array4 mutableCopy]; NSLog(@"%p",array6);
2016-08-23 10:54:50.878 [1364:147504] 0x10409cc90 2016-08-23 10:54:53.636 [1364:147504] 0x10409cc90 2016-08-23 10:54:53.636 [1364:147504] 0x7fd602d1c330 2016-08-23 10:54:54.322 [1364:147504] 0x7fd602dae190 2016-08-23 10:54:54.323 [1364:147504] 0xa000000003332313 2016-08-23 10:54:54.323 [1364:147504] 0x7fd602e07420 2016-08-23 10:54:55.924 [1364:147504] 0x7fd602d00d60 2016-08-23 10:54:56.750 [1364:147504] 0x7fd602d00d60 2016-08-23 10:54:56.750 [1364:147504] 0x7fd602c11050 2016-08-23 10:54:56.751 [1364:147504] 0x7fd602c2bfc0 2016-08-23 10:54:56.751 [1364:147504] 0x7fd602c0a070 2016-08-23 10:54:56.751 [1364:147504] 0x7fd602c0a220
3、NSHashTable -NSMapTable
NSHashTable 和 -NSMapTable是iOS 6 后出现的容器类对象，他有一个特点就是，对加入其中的对象，可以设置其为弱引用,
而不是像数组等容器加入对象后默认对象引用计数会加1，强引用，有点类似（weak,assgin）的容器
- (instancetype)initWithOptions:(NSPointerFunctionsOptions)options capacity:(NSUInteger)initialCapacity NS_DESIGNATED_INITIALIZER; typedef NS_OPTIONS(NSUInteger, NSPointerFunctionsOptions) { // Memory options are mutually exclusive // default is strong NSPointerFunctionsStrongMemory NS_ENUM_AVAILABLE(10_5, 6_0) = (0UL << 0), // use strong write-barrier to backing store; use GC memory on copyIn #if (TARGET_OS_MAC && !(TARGET_OS_EMBEDDED || TARGET_OS_IPHONE)) || TARGET_OS_WIN32 NSPointerFunctionsZeroingWeakMemory NS_ENUM_DEPRECATED_MAC(10_5, 10_8) = (1UL << 0), // deprecated; uses GC weak read and write barriers, and dangling pointer behavior otherwise #endif NSPointerFunctionsOpaqueMemory NS_ENUM_AVAILABLE(10_5, 6_0) = (2UL << 0), NSPointerFunctionsMallocMemory NS_ENUM_AVAILABLE(10_5, 6_0) = (3UL << 0), // free() will be called on removal, calloc on copyIn NSPointerFunctionsMachVirtualMemory NS_ENUM_AVAILABLE(10_5, 6_0) = (4UL << 0), NSPointerFunctionsWeakMemory NS_ENUM_AVAILABLE(10_8, 6_0) = (5UL << 0), // uses weak read and write barriers appropriate for ARC or GC // Personalities are mutually exclusive // default is object. As a special case, 'strong' memory used for Objects will do retain/release under non-GC NSPointerFunctionsObjectPersonality NS_ENUM_AVAILABLE(10_5, 6_0) = (0UL << 8), // use -hash and -isEqual, object description NSPointerFunctionsOpaquePersonality NS_ENUM_AVAILABLE(10_5, 6_0) = (1UL << 8), // use shifted pointer hash and direct equality NSPointerFunctionsObjectPointerPersonality NS_ENUM_AVAILABLE(10_5, 6_0) = (2UL << 8), // use shifted pointer hash and direct equality, object description NSPointerFunctionsCStringPersonality NS_ENUM_AVAILABLE(10_5, 6_0) = (3UL << 8), // use a string hash and strcmp, description assumes UTF-8 contents; recommended for UTF-8 (or ASCII, which is a subset) only cstrings NSPointerFunctionsStructPersonality NS_ENUM_AVAILABLE(10_5, 6_0) = (4UL << 8), // use a memory hash and memcmp (using size function you must set) NSPointerFunctionsIntegerPersonality NS_ENUM_AVAILABLE(10_5, 6_0) = (5UL << 8), // use unshifted value as hash & equality NSPointerFunctionsCopyIn NS_ENUM_AVAILABLE(10_5, 6_0) = (1UL << 16), // the memory acquire function will be asked to allocate and copy items on input };
4、iOS 中的Keychain API
ios 中的keychian 应该是一个系统级的单例，在里面存的信息，安全的程度比较高，
不同的app可以通过相同的key,度取相关的信息，简单实现不同app之间的信息共享一种思路