前言

autorelease的规范：
0）创建对象，将对象存储到自动释放池之中，就不需要再去手动的release。

一、一般情况下，写1个类，会为我们的类写1个类方法，用来让外界调用类方法来快速的得到1个对象

例如：有一个Pig类：
@interface Pig : NSObject
@property(nonatomic,retain)NSString *name;
@property(nonatomic,assign)int age;
@property(nonatomic,assign)float weight;

– (instancetype)initWithName:(NSString *)name andAge:(int)age andWeight:(float)weight;

++(instancetype)pig;

++(instancetype)pigWithName:(NSString *)name andAge:(int)age andWeight:(float)weight;
@end

@implementation Pig
– (void)dealloc
{
NSLog(@“猪挂了。。。”);
[_name release];
[super dealloc];
}
– (instancetype)initWithName:(NSString *)name andAge:(int)age andWeight:(float)weight
{
if(self = [super init])
{