iOSRuntime的成员与属性

一、成员变量

1.1 Ivar

Ivar: 实例变量类型，是一个指向objc_ivar结构体的指针

typedef struct objc_ivar *Ivar;

而objc_ivar的定义如下

struct objc_ivar {
    char *ivar_name                                          OBJC2_UNAVAILABLE;
    char *ivar_type                                          OBJC2_UNAVAILABLE;
    int ivar_offset                                          OBJC2_UNAVAILABLE;
#ifdef __LP64__
    int space                                                OBJC2_UNAVAILABLE;
#endif
}

1.2 常用方法

// 获取所有成员变量
class_copyIvarList

// 获取所有方法
class_copyMethodList

// 获取所有属性
ivar_getName

// 获取成员变量类型编码
ivar_getTypeEncoding

// 获取指定名称的成员变量
class_getInstanceVariable

// 获取某个对象成员变量的值
object_getIvar

// 设置某个对象成员变量的值
object_setIvar

1.3 class_copyPropertyList与class_copyIvarList区别

class_copyPropertyList：仅仅返回属性
class_copyIvarList：不仅返回属性，还返回变量({}修饰的变量)

//XYPerson.h
#import <Foundation/Foundation.h>

@interface XYPerson : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) NSUInteger age;
@end

//XYPerson.m
#import "XYPerson.h"

@interface XYPerson (){
    NSInteger sex;
}

@property (nonatomic, copy) NSString *hobby;

@end

@implementation XYPerson

//MainController.m
- (void)viewDidLoad {
    XYPerson *person = [XYPerson new];
    
    {
        //记录属性的个数
        unsigned int count = 0;
        
        //获取属性列表
        Ivar *members = class_copyIvarList([person class], &count);
        
        //遍历属性列表
        for (NSInteger i = 0; i < count; i++) {
            
            //取到属性
            Ivar ivar = members[i];
            
            //获取属性名
            const char *memberName = ivar_getName(ivar);
            NSString *ivarName = [NSString stringWithFormat:@"%s", memberName];
            
            NSLog(@"属性名:%@", ivarName);
            
        }
        free(members);
    }
    
    NSLog(@"----------");
  
    {
        //记录属性的个数
        unsigned int count = 0;
        objc_property_t *properties = class_copyPropertyList([person class], &count);
        //遍历属性列表
        for (NSInteger i = 0; i < count; i++) {
            
            //取到属性
            objc_property_t property = properties[i];
            
            //获取属性名
            NSString * propertyName = [NSString stringWithCString:property_getName(property) encoding:NSUTF8StringEncoding];
            
            NSLog(@"属性名:%@", propertyName);
        }
        free(properties);
    }
}

打印如下

2018-03-07 11:26:29.693788+0800 tableView[76444:1687311] 属性名:sex
2018-03-07 11:26:29.694058+0800 tableView[76444:1687311] 属性名:_name
2018-03-07 11:26:29.694371+0800 tableView[76444:1687311] 属性名:_age
2018-03-07 11:26:29.694485+0800 tableView[76444:1687311] 属性名:_hobby
2018-03-07 11:26:29.694636+0800 tableView[76444:1687311] ----------
2018-03-07 11:26:29.694766+0800 tableView[76444:1687311] 属性名:hobby
2018-03-07 11:26:29.694913+0800 tableView[76444:1687311] 属性名:name
2018-03-07 11:26:29.695080+0800 tableView[76444:1687311] 属性名:age

可见class_copyIvarList还获取了一个变量sex

二、获取类的私有属性和私有方法

有一个XYPerson类

//XYPerson.h
#import <Foundation/Foundation.h>

@interface XYPerson : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) NSUInteger age;
- (void)printInfo;

@end

//XYPerson.m
#import "XYPerson.h"

@interface XYPerson (){
    NSInteger sex;
}

@property (nonatomic, copy) NSString *hobby;

- (void)_privateMethod;

@end

@implementation XYPerson

- (void)_privateMethod{
    NSLog(@"_privateMethod");
}

- (void)printInfo{
   NSLog(@"printInfo");
}

2.1 获取类的私有方法

//MainController.m
- (void)viewDidLoad {
    [super viewDidLoad];

    unsigned int count = 0;
    Method *methods = class_copyMethodList([XYPerson class], &count);
    for (int i = 0; i < count; i++) { // 3
        NSLog(@"%s", sel_getName(method_getName(methods[i]))); // 4
    } // 5
    free(methods); // 6
}

打印：

2018-03-07 11:01:14.867925+0800 tableView[75802:1660458] _privateMethod
2018-03-07 11:01:14.868151+0800 tableView[75802:1660458] hobby
2018-03-07 11:01:14.868295+0800 tableView[75802:1660458] setHobby:
2018-03-07 11:01:14.868550+0800 tableView[75802:1660458] printInfo
2018-03-07 11:01:14.868742+0800 tableView[75802:1660458] .cxx_destruct
2018-03-07 11:01:14.868884+0800 tableView[75802:1660458] name
2018-03-07 11:01:14.869020+0800 tableView[75802:1660458] setName:
2018-03-07 11:01:14.869117+0800 tableView[75802:1660458] setAge:
2018-03-07 11:01:14.869215+0800 tableView[75802:1660458] age

你会发现有个.cxx_destruct方法，这玩意儿大有来头

ARC actually creates a -.cxx_destruct method to handle freeing instance variables. This method was originally created for calling C++ destructors automatically when an object was destroyed.
When the compiler saw that an object contained C++ objects, it would generate a method called .cxx_destruct. ARC piggybacks on this method and emits the required cleanup code within it.

可以了解到，.cxx_destruct方法原本是为了C++对象析构的，ARC借用了这个方法插入代码实现了自动内存释放的工作，详细介绍可看sunnyxx大神的

2.2 获取类的私有属性

使用KVC的valueForKey

//MainController.h
- (void)viewDidLoad {
    [super viewDidLoad];
    XYPerson *person = [XYPerson new];
    [person setValue:@"make love" forKey:@"hobby"];
    NSString *propertyName = [person valueForKey:@"hobby"];
    NSLog(@"属性：%@", propertyName);
}

那么问题来了，KVC是怎么实现的呢，请移步这里

使用runtime的class_copyIvarList拿到所有的属性，非常的，简单粗暴！

- (void)viewDidLoad {
    [super viewDidLoad];
    
    XYPerson *person = [XYPerson new];
    
    //记录属性的个数
    unsigned int count = 0;
    
    //获取属性列表
    Ivar *members = class_copyIvarList([person class], &count);
    
    //遍历属性列表
    for (NSInteger i = 0; i < count; i++) {
        
        //取到属性
        Ivar ivar = members[i];
        
        //获取属性名
        const char *memberName = ivar_getName(ivar);
        NSString *ivarName = [NSString stringWithFormat:@"%s", memberName];        
        NSLog(@"属性名:%@", ivarName);
    }  
    free(members);
}

使用runtime的class_getInstanceVariable和object_setIvar，直捣黄龙!

Ivar ivar = class_getInstanceVariable([XYPerson class], "_hobby");    
XYPerson *person = [XYPerson new];
object_setIvar(person, ivar, @"make love");
NSString * propertyName = object_getIvar(person, ivar);
NSLog(@"属性名:%@", propertyName);

打印如下：

2018-03-07 10:33:19.989501+0800 tableView[75120:1626828] 属性名:make love

使用object_getInstanceVariable，不过ARC下不可用，MRC下可以用，🙄

NSString *propertyName;
XYPerson *person = [XYPerson new];
object_getInstanceVariable(person, "_hobby", (void *)&propertyName);
NSLog(@"属性名:%@", propertyName);

而且object_getIvar还快一些，根据苹果的注释

* @note \c object_getIvar is faster than \c object_getInstanceVariable if the Ivar
 *  for the instance variable is already known.

三、简化initWithCoder的代码

不使用runtime，需要一个一个的写

//AddressModel.m
#import "AddressModel.h"

@implementation AddressModel

- (id)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super init]) {
        _name = [aDecoder decodeObjectForKey:@"name"];
        _selected = [aDecoder decodeBoolForKey:@"selected"];
        _lat = [aDecoder decodeDoubleForKey:@"lat"];
        _lng = [aDecoder decodeDoubleForKey:@"lng"];
         
        
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {    
    [aCoder encodeObject:_name forKey:@"name"];
    [aCoder encodeBool:_selected forKey:@"selected"];
    [aCoder encodeDouble:_lat forKey:@"lat"];
    [aCoder encodeDouble:_lng forKey:@"lng"];    
}

使用了runtime，爽歪歪

#import "AddressModel.h"
#import <objc/runtime.h>

@implementation AddressModel

- (id)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super init]) {        
        unsigned int count = 0;
        Ivar *members = class_copyIvarList([self class], &count);
        for (NSInteger i = 0; i < count; i++) {
            Ivar ivar = members[i];
            const char *memberName = ivar_getName(ivar);
            NSString *key = [[NSString alloc] initWithUTF8String:memberName];
            [self setValue:[aDecoder decodeObjectForKey:key] forKey:key];
        }
        free(members);        
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {
    unsigned int count = 0;
    Ivar *members = class_copyIvarList([self class], &count);
    for (NSInteger i = 0; i < count; i++) {
        Ivar ivar = members[i];
        const char *memberName = ivar_getName(ivar);
        NSString *key = [[NSString alloc] initWithUTF8String:memberName];
        id value = [self valueForKey:key];        
        [aCoder encodeObject:[self valueForKey:key] forKey:key];
    }
}

这里使用initWithCoder是为了遵循NSCoding协议，以便进行持久化存储，持久化存储有NSKeyedArchiver与NSUserDefaults两种方案

NSKeyedArchiver

//

- (void)viewDidLoad {
    [super viewDidLoad];
    AddressModel *address = [AddressModel new];
    address.name = @"世贸中心";
    address.selected = NO;
    address.lat = 13.89773;
    address.lng = 31.87878;

    [NSKeyedArchiver archiveRootObject:address toFile:[[self class] savePath]];
    NSData *storedData = [NSKeyedUnarchiver unarchiveObjectWithFile:[[self class] savePath]];
}
+ (NSString *)savePath{
    NSString *docPath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject];
    NSString *path=[docPath stringByAppendingPathComponent:@"userAddresses"];
    return path;
}

image.png

NSUserDefaults


- (void)viewDidLoad {
    NSData *theData = [NSKeyedArchiver archivedDataWithRootObject:address];
    [[NSUserDefaults standardUserDefaults] setObject:theData forKey:@"addressModel"];
    [[NSUserDefaults standardUserDefaults] synchronize];
    NSData *bufferData = [[NSUserDefaults standardUserDefaults] objectForKey:@"addressModel"];
    NSData *storedData = [NSKeyedUnarchiver unarchiveObjectWithData:bufferData];
}