1、提问：甲乙丙分别输出的retainCount为多少？
NSMutableArray* ary = [[NSMutableArray array] retain];
NSString *str = [NSString stringWithFormat:@"test"];//1 __NSCFString， 在 <Foundation/Foundation.h>框架下-1 NSTaggedPointerString，如果长度超过一定范围或者为中文时，引用计数为1__NSCFString
---此处特别说明，当 NSString *str = @“test”;这种方式创建时 __NSCFConstantString，引用计数在 <Foundation/Foundation.h>框架下 -1，否则
18446744073709551615
[str retain];//+1
[ary addObject:str];//+1
NSLog(@"甲------%@%ld",str,[str retainCount]);//3
[str retain];//+1
[str release];//-1
[str release];//-1
NSLog(@"乙------%@%ld",str,[str retainCount]);//2
[ary removeAllObjects];//-1
NSLog(@"丙------%@%ld",str,[str retainCount]);//1
2、NSArray，NSMutableArray
NSArray * array = [NSArray array];// -1 __NSArray0
[array retain];//-1
NSArray * array1 = [NSArray arrayWithObject:@"1"];//1 __NSArrayI
NSMutableArray * array3 = [NSMutableArray array];//1 __NSArrayM
NSMutableArray * array4 = [NSMutableArray arrayWithObject:@"1"];//1 __NSArrayM
3、NSNumber
NSNumber *num1 = @(100);// __NSCFNumber9223372036854775807
NSNumber *num2 = [[NSNumber alloc] initWithInt:1000000];// __NSCFNumber9223372036854775807
以上关于NSString的解释，因为会出现多种情况，欢迎交流。