iOS中的内存管理1-白红宇

iOS中的内存管理1

阅读量：4562 次

发布时间：2019-06-08

本文共 3467 字，大约阅读时间需要 11 分钟。

#import 
     
      #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 
     
      @interface Person : NSObject
      
       @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

转载于:https://www.cnblogs.com/wohaoxue/p/4725506.html

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