self.nsme 和 _name 的问题

.h文件
@interface myclass:NSObject
@property(nonatomic,retain)NSArray*MyArray;
@end

.m文件
@implementation myclass
-(void)viewDidLoad
{
  [superviewDidLoad];

  _MyArray=[[NSArrayalloc]initWithObjects:@"",nil];
  NSLog(@"%lu",(unsignedlong)[self.MyArray retainCount]);//输出1

  self.MyArray=[[NSArrayalloc]initWithObjects:@"",nil];
  NSLog(@"%lu",(unsignedlong)[self.MyArray retainCount]);//输出2

  我的理解是
  self.MyArray=[[NSArrayalloc]initWithObjects:@"",nil];
  相当于
  NSArray*a=[[NSArrayalloc]initWithObjects:@"",nil];
  self. MyArray =a;
  而self.MyArray会调用myArray的set方法，
    -(void)setMyArray:( NSArray *)Array
   {
      if(Array!= MyArray)
     {
        [MyArray release];
        MyArray =[Array retain];
     }
  }

}