iOS中的内存管理1

#import <Foundation/Foundation.h>
#import "Person.h"
int main(int argc, const char * argv[]) {
//    @autoreleasepool {
//        
//        Person *p = [[Person alloc] initWithName:@"池" gender:@"nan" age:18];
//        NSLog(@"%lu",[p retainCount]);
//        
//        
//        NSLog(@"--------------");
//        Person *p1 = [p retain];
//        NSLog(@"%lu",[p retainCount]);
//        NSLog(@"%lu",[p1 retainCount]);
//        
//        NSLog(@"--------------");
//        
//        Person *p2 = [p1 retain];
//        NSLog(@"%lu",[p retainCount]);
//        NSLog(@"%lu",[p1 retainCount]);
//        NSLog(@"%lu",[p2 retainCount]);
//        
//        NSLog(@"--------------");
//        //release 让对象的引用计数立即 -1
//        [p release];
//        NSLog(@"%lu", [p retainCount]);
//        [p release];
//        NSLog(@"%lu", [p retainCount]);
//        [p release];
//        NSLog(@"%lu", [p retainCount]);// 错误的
//        //谁才有引用计数的概念:
//        //1.堆区空间才有引用计数的概念
//        //2.堆区的对象才会有引用计数
//    
//    }
//    Person *p = [[Person alloc] initWithName:@"张三" gender:@"男" age:18];
//    NSLog(@"%lu", [p retainCount]);
//    [p retain];
//    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
//    
//    
//    
//    [p autorelease];
//    
//    NSLog(@"%lu",[p retainCount]);
//    
//    
//    
//    [pool release];
//     NSLog(@"%lu",[p retainCount]);
//    
    
    
    //企业级题
//    @autoreleasepool {
//        for (long i = 0; i < 100000000; i++) {
//            @autoreleasepool {
//                Person *per = [[Person alloc] init];
//                [per autorelease];
//            }
//        }
//    }
    
    //内存管理原则:当你对一个对象进行了 alloc, retain, copy 操作,你就对该对象拥有了所有权,要对该对象负责,对其进行release,或者autorelease操作
    //在一个方法内部,要保证对象的+ 和 - 相等.
    
    
    //创建Person对象
    @autoreleasepool {
        Person *p = [Person personWithName:@"张三" gender:@"男" age:44];
        Person *p1 = [p copy];
        
        [p1 sayHi];
        [p1 release];
    }
   
    
    //内存问题:
    //1.野指针错误:最后一个release玩,空间已经被系统回收,如果再访问,就是访问一块没有所有权的空间,出现野指针,野指针不会立即报错,但是存在安全隐患,另外,错误不容易排错.
    //2.过度释放:对一块没有所有权的空间进行释放空间,会造成程序的立即crash;
    //3.内存泄露:对一块拥有所有权的空间,使用完之后没有释放,此时存在安全隐患,当内存泄露足够多得时候,造成程序的crash;
    return 0;
}

person.h

#import <Foundation/Foundation.h>

@interface Person : NSObject<NSCopying>
@property (nonatomic,retain) NSString *name;
@property (nonatomic,retain) NSString *gender;
@property (nonatomic,assign) NSInteger age;

- (instancetype)initWithName:(NSString *)name gender:(NSString *)gender age:(NSInteger)age;
+ (instancetype)personWithName:(NSString *)name gender:(NSString *)gender age:(NSInteger)age;
- (void)sayHi;
@end

person.m

#import "Person.h"

@implementation Person
- (instancetype)initWithName:(NSString *)name gender:(NSString *)gender age:(NSInteger)age
{
    if (self = [super init]) {
        self.name = name;
        self.gender = gender;
        self.age = age;
    }
    return self;
}

+ (instancetype)personWithName:(NSString *)name gender:(NSString *)gender age:(NSInteger)age{
    return [[[self alloc] initWithName:name gender:gender age:age] autorelease];
    
}
- (void)sayHi
{
    NSLog(@"sayHigoggo");
}
//当对一个兑现copy时,会自动调用该方法,用来创建新的对象,复制内容
- (id)copyWithZone:(NSZone *)zone
{
    //1.创建新的对象
    Person *newPer = [[Person allocWithZone:zone] init];
    //2.拷贝内容
    newPer.name = self.name;
    newPer.age = self.age;
    newPer.gender = self.gender;
    //3.返回新的对象
    return newPer;
}
//当对象的引用计数为0是系统会自动调用,切记不要人为调用
- (void)dealloc
{
    NSLog(@"%@回收了",self);
    [super dealloc];
}
@end