一、MRC内存管理
- assign:修饰基本数据类型，setter方法就直接赋值，不会先释放旧对象再进行赋值。
- retain:修饰OC对象，setter方法需要先释放旧对象再赋值新对象。
二、Copy、mutableCopy
拷贝的目的：产生一个副本对象，跟源对象互不影响。
Copy:不可变拷贝，产生不可变副本。
mutableCopy:可变拷贝，产生可变副本。
深拷贝：内容拷贝，产生新的对象。
浅拷贝：指针拷贝，不会产生新的对象。
在MRC环境下使用copy、mutableCopy会进行retain操作，所以要进行release操作。
mutalbeCopy:只针对系统Foundation框架下的类进行的操作，属性只要copy操作，因为属性是不确定的类，要保持通用性。-
1.系统类的拷贝
-
2.自定义类的拷贝
- 1.自定义的类要遵守NSCopying协议
- *2.实现协议中的- (id)copyWithZone:(nullable NSZone )zone;方法
---------------------------------------------------MJPerson.h----------------------------------------------
#import <Foundation/Foundation.h>
@interface MJPerson : NSObject <NSCopying>
@property (assign, nonatomic) int age;
@property (assign, nonatomic) double weight;
@end
---------------------------------------------------MJPerson.m----------------------------------------------
#import "MJPerson.h"
@implementation MJPerson
- (id)copyWithZone:(NSZone *)zone
{
MJPerson *person = [[MJPerson allocWithZone:zone] init];
person.age = self.age;
// person.weight = self.weight;
return person;
}
- (NSString *)description
{
return [NSString stringWithFormat:@"age = %d, weight = %f", self.age, self.weight];
}
@end
--------------------------------------------------main.m-----------------------------------------------
#import <Foundation/Foundation.h>
#import "MJPerson.h"
int main(int argc, const char * argv[]) {
@autoreleasepool {
MJPerson *p1 = [[MJPerson alloc] init];
p1.age = 20;
p1.weight = 50;
MJPerson *p2 = [p1 copy];
p2.age = 30;
NSLog(@"%@", p1);
NSLog(@"%@", p2);
[p2 release];
[p1 release];
}
return 0;
}
三、引用计数的存储
objc源码分析
四、weak指针的原理
objc源码分析
五、autorelease原理
#import <Foundation/Foundation.h>
#import "MJPerson.h"
int main(int argc, const char * argv[]) {
@autoreleasepool {
// atautoreleasepoolobj = objc_autoreleasePoolPush();
for (int i = 0; i < 1000; i++) {
MJPerson *person = [[[MJPerson alloc] init] autorelease];
} // 8000个字节
// objc_autoreleasePoolPop(atautoreleasepoolobj);
}
return 0;
}
/*
struct __AtAutoreleasePool {
__AtAutoreleasePool() { // 构造函数，在创建结构体的时候调用
atautoreleasepoolobj = objc_autoreleasePoolPush();
}
~__AtAutoreleasePool() { // 析构函数，在结构体销毁的时候调用
objc_autoreleasePoolPop(atautoreleasepoolobj);
}
void * atautoreleasepoolobj;
};
{
__AtAutoreleasePool __autoreleasepool;
MJPerson *person = ((MJPerson *(*)(id, SEL))(void *)objc_msgSend)((id)((MJPerson *(*)(id, SEL))(void *)objc_msgSend)((id)((MJPerson *(*)(id, SEL))(void *)objc_msgSend)((id)objc_getClass("MJPerson"), sel_registerName("alloc")), sel_registerName("init")), sel_registerName("autorelease"));
}
atautoreleasepoolobj = objc_autoreleasePoolPush();
MJPerson *person = [[[MJPerson alloc] init] autorelease];
objc_autoreleasePoolPop(atautoreleasepoolobj);
*/
六、RunLoop与autorelease
#import "ViewController.h"
#import "MJPerson.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// 这个Person什么时候调用release，是由RunLoop来控制的
// 它可能是在某次RunLoop循环中，RunLoop休眠之前调用了release
// MJPerson *person = [[[MJPerson alloc] init] autorelease];
MJPerson *person = [[MJPerson alloc] init];
NSLog(@"%s", __func__);
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
NSLog(@"%s", __func__);
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
NSLog(@"%s", __func__);
}
/*
typedef CF_OPTIONS(CFOptionFlags, CFRunLoopActivity) {
kCFRunLoopEntry = (1UL << 0), 1
kCFRunLoopBeforeTimers = (1UL << 1), 2
kCFRunLoopBeforeSources = (1UL << 2), 4
kCFRunLoopBeforeWaiting = (1UL << 5), 32
kCFRunLoopAfterWaiting = (1UL << 6), 64
kCFRunLoopExit = (1UL << 7), 128
kCFRunLoopAllActivities = 0x0FFFFFFFU
};
*/
/*
kCFRunLoopEntry push
<CFRunLoopObserver 0x60000013f220 [0x1031c8c80]>{valid = Yes, activities = 0x1, repeats = Yes, order = -2147483647, callout = _wrapRunLoopWithAutoreleasePoolHandler (0x103376df2), context = <CFArray 0x60000025aa00 [0x1031c8c80]>{type = mutable-small, count = 1, values = (\n\t0 : <0x7fd0bf802048>\n)}}
kCFRunLoopBeforeWaiting | kCFRunLoopExit
kCFRunLoopBeforeWaiting: pop、push
kCFRunLoopExit pop
<CFRunLoopObserver 0x60000013f0e0 [0x1031c8c80]>{valid = Yes, activities = 0xa0, repeats = Yes, order = 2147483647, callout = _wrapRunLoopWithAutoreleasePoolHandler (0x103376df2), context = <CFArray 0x60000025aa00 [0x1031c8c80]>{type = mutable-small, count = 1, values = (\n\t0 : <0x7fd0bf802048>\n)}}
*/
@end
`
