Runtime学习笔记

作者: LD_左岸 | 来源:发表于2017-12-30 09:13 被阅读23次

一.消息机制

OC调用方法是动态调用调用未实现的方法编译不报错方法调用的本质是发送消息

import <objc/message.h>
[p eat];
[p performSelector:@selector(eat)];

objc_msgSend();
Xcode5之后使用运行时可设置
objc_msgSend(p, @selector(eat:),@"🎃");//传递参数

F36AF365-C511-49F8-B00E-AE53EF06A8E9.png

方法调用的本质是执行performSelector 把一个方法名转化成一个方法编号根据这个方法编号去方法列表中查找对应的方法调用方法的实现

二.交换方法

参考https://www.jianshu.com/p/9e3cf04f3dc8

#import <Foundation/Foundation.h>
@interface NSArray (ldd)

@end

#import "NSArray+ldd.h"
#import <objc/message.h>
@implementation NSArray (ldd)
//const char * const LD_Key = "Key";
+ (void)load
{
    [super load];
    
    Method fromMethod = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(objectAtIndex:));
    Method toMethod = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(ldd_objectAtIndex:));
    method_exchangeImplementations(fromMethod, toMethod);
    
    Method fromMutMethod = class_getInstanceMethod(objc_getClass("__NSArrayM"), @selector(objectAtIndex:));
    Method toMutMethod = class_getInstanceMethod(objc_getClass("__NSArrayM"), @selector(ldd_mutaObjectAtIndex:));
    method_exchangeImplementations(fromMutMethod, toMutMethod);
}
- (id)ldd_objectAtIndex:(NSUInteger)index
{
    if (index < self.count) {
        return [self ldd_objectAtIndex:index];
    }else{
        return nil;
    }
}
- (id)ldd_mutaObjectAtIndex:(NSUInteger)index
{
    if (index < self.count) {
        return [self ldd_mutaObjectAtIndex:index];
    }else{
        return nil;
    }
}
@end

三.动态添加方法

Person * p = [[Person alloc]init];
 //[p eat]; //编译不过
//动态添加方法
 [p performSelector:@selector(eat) withObject:nil];//编译的过 运行崩

//
//  Person.m
//  test
//
//  Created by 李洞洞 on 27/12/17.
//  Copyright © 2017年 Minte. All rights reserved.
//

#import "Person.h"
#import <objc/message.h>
@implementation Person
void ldd(id ldself,SEL ldsel){
    NSLog(@"这是一个动态添加的方法");
    NSLog(@"%@ -- %@",[ldself class],NSStringFromSelector(ldsel));
};
//调用时刻：当在外界调用了当前类未实现的方法时调用
+ (BOOL)resolveClassMethod:(SEL)sel
{
    return [super resolveClassMethod:sel];
}

+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    if (sel == NSSelectorFromString(@"eat")) {
//IMP:方法的实现 函数的入口 函数名 函数指针
//types:方法的类型
        class_addMethod([self class], @selector(eat), (IMP)ldd, "V@:");
    }
    return [super resolveInstanceMethod:sel];
}
@end

1385290-b085510875abb98d.png

#pragma mark -- 动态添加方法
    Person * p = [[Person alloc]init];
    [p performSelector:@selector(eat:) withObject:@"🎃"];

#import "Person.h"
#import <objc/message.h>
@implementation Person
void ldd(id ldself,SEL ldsel,id some){
    NSLog(@"这是一个动态添加的方法");
    NSLog(@"%@ -- %@",[ldself class],NSStringFromSelector(ldsel));
};
+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    if (sel == NSSelectorFromString(@"eat:")) {
        class_addMethod([self class], @selector(eat:), (IMP)ldd, "V@:@");
    }
    return [super resolveClassMethod:sel];
}

四.动态添加属性

#import <UIKit/UIKit.h>

@interface UIButton (ldd)
/*
 不生成_ld_Title
 不生成 ld_Title的set get
 */
@property NSString * ld_Title;
@end

#import "UIButton+ldd.h"
#import <objc/message.h>
@implementation UIButton (ldd)
const char * const LD_Key = "Key";
- (void)setLd_Title:(NSString *)ld_Title
{
    objc_setAssociatedObject(self, LD_Key, ld_Title, OBJC_ASSOCIATION_COPY_NONATOMIC);
}
- (NSString*)ld_Title
{

    return objc_getAssociatedObject(self, LD_Key);
}
@end

如果不用以上的写法手动实现set get方法也可以不好的地方是：
静态全局变量来保存值如果我这个对象销毁了这个变量保存的值还在此时你变量保存的值和对象之间并没任何关系和我这个对象无关了。最好的状态是我这个对象在这个属性在对象不在属性也不在。

 #pragma mark -- 动态添加属性
 UIButton * btn = [[UIButton alloc]init];
 btn.ld_Title = @"ldd";
 NSLog(@"%@",btn.ld_Title);
 btn.ld_Title = @"999";
 NSLog(@"%@",btn.ld_Title);

或者这么玩

static char * const LD_Key = "Key";
static char * const LD_ButtonKey = "ButtonKey";
- (void)viewDidLoad {
    [super viewDidLoad];
    
    UIButton * button = ({
        UIButton * btn = [[UIButton alloc]init];
        objc_setAssociatedObject(btn, LD_ButtonKey, @"6666", OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        btn;
    });
    [self.view addSubview:button];
    
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        NSLog(@"%@",objc_getAssociatedObject(button, LD_ButtonKey));
    });

    
    
    UIView * view1 = ({
        UIView * view = [[UIView alloc]initWithFrame:CGRectMake(10, 10, 100, 100)];
        view.backgroundColor = [UIColor redColor];
        UITapGestureRecognizer * tap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(view1Click:)];
        NSDictionary * value= @{@"color":[UIColor greenColor]};
        objc_setAssociatedObject(view, LD_Key, value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        [view addGestureRecognizer:tap];
        view;
    });
    [self.view addSubview:view1];
}
- (void)view1Click:(UITapGestureRecognizer*)tap
{
    UIView * view = tap.view;
    NSDictionary *value = objc_getAssociatedObject(view, LD_Key);
    view.backgroundColor = value[@"color"];
}
@end

五.字典转模型

#import <Foundation/Foundation.h>
@protocol LDModel <NSObject>
@optional

/**
 模型字段是数组

 @return {模型字段 : 数组中存储的自定义模型的类名}
 */
+ (NSDictionary *)objectClassInArray;

/**
 模型中特殊字段(id...)的替换

 @return {模型中的字段:字典中的特殊字段}
 */
+ (NSDictionary *)propertykeyReplacedWithValue;
@end

@interface NSObject (Prepory)<LDModel>
+ (id)modelWithDict:(NSDictionary*)dict;
@end

#import "NSObject+Prepory.h"
#import <objc/message.h>
@implementation NSObject (Prepory)
+ (id)modelWithDict:(NSDictionary *)dict
{
    id object = [[self alloc]init];
    unsigned int count = 0;
    Ivar * ivarList = class_copyIvarList([self class], &count);
    for (int i = 0; i < count; i++) {
        Ivar  ivar = ivarList[i];
        char const *  name = ivar_getName(ivar);
        NSString * ocName = [NSString stringWithUTF8String:name];
        NSString * key = [ocName substringFromIndex:1];
        id value = nil;
        if ([self respondsToSelector:@selector(propertykeyReplacedWithValue)]) {
            key = [[self propertykeyReplacedWithValue]objectForKey:key];
            
            if (!key) {
                key = [ocName substringFromIndex:1];
            }

            value = dict[key];
            
        }
         key = [ocName substringFromIndex:1];
        
        const char * name1 = ivar_getTypeEncoding(ivar);
        NSString * newName = [[NSString alloc]initWithUTF8String:name1];
        
        
        if ([value isKindOfClass:[NSDictionary class]]&&![key hasPrefix:@"NS"]) {
            newName = [newName stringByReplacingOccurrencesOfString:@"\"" withString:@""];
            newName = [newName stringByReplacingOccurrencesOfString:@"@" withString:@""];
            Class class = NSClassFromString(newName);
            id val = [class modelWithDict:value];
            [object setValue:val forKey:key];
            
            }else if ([value isKindOfClass:[NSArray class]]&&![key hasPrefix:@"NS"]){
                
                if ([self respondsToSelector:@selector(objectClassInArray)]) {
                    id propertyValueType = [[self objectClassInArray] objectForKey:key];
                    Class clas = NSClassFromString(propertyValueType);
                    NSArray * arr = (NSArray*)value;
                    id obj = nil;
                    NSMutableArray * muArr = [NSMutableArray array];
                    for (int i = 0; i < arr.count; i++) {
                       obj = [clas modelWithDict:arr[i]];//key里面放的是区县模型//这是一个模型
                        [muArr addObject:obj];
                    }
                    [object setValue:muArr forKey:key];

                }
                
                
            }else if (value) {

                
                [object setValue:value forKey:key];
                
            }
               
    }
    free(ivarList);
    return object;
}
@end

六.KVO的底层实现

当某个类的属性对象第一次被观察时，系统就会在运行期间动态地创建该类的一个派生类，在这个派生类中重写基类的任何被观察属性的setter方法。派生类在被重写的setter方法内实现真正的通知机制
如果原类为Person，那么生成的派生类名为NSKVONotifying_Person。

每一个类中都有一个isa指针指向当前类，所有系统就是在当一个类的对象第一次被观察的时候，系统就会将isa指针指向动态生成的派生类，从而在被监听属性赋值时被执行的是派生类的setter方法

键值观察通知依赖于NSObject 的两个方法: willChangeValueForKey: 和 didChangevlueForKey:;在一个被观察属性发生改变之前， willChangeValueForKey: 一定会被调用，这就会记录旧的值。而当改变发生后，didChangeValueForKey: 会被调用，继而 observeValueForKey: ofObject: change: context: 也会被调用。

七.归档&解档

#import <Foundation/Foundation.h>
@interface Person : NSObject<NSCoding>
@property (nonatomic,copy) NSString *name;
@property (nonatomic,copy) NSString *age;
@property (nonatomic,copy) NSString *height;
@end

#import "Person.h"
#import <objc/message.h>
@implementation Person
- (void)encodeWithCoder:(NSCoder *)aCoder
{
    unsigned int count = 0;
    Ivar * ivars = class_copyIvarList([self class], &count);
    for (int i = 0; i < count; i ++) {
        Ivar ivar = ivars[i];
        const char * name = ivar_getName(ivar);
        NSString * key = [NSString stringWithUTF8String:name];
        id value = [self valueForKey:key];
        //归档
        [aCoder encodeObject:value forKey:key];
    }
}
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super init]) {
        unsigned int count = 0;
        Ivar * ivars = class_copyIvarList([self class], &count);
        for (int i = 0; i < count; i ++) {
            Ivar ivar = ivars[i];
            const char * name = ivar_getName(ivar);
            NSString * key = [NSString stringWithUTF8String:name];
           //解档
            id value = [aDecoder decodeObjectForKey:key];
            [self setValue:value forKey:key];
        }
    }
    return self;
}
@end

- (void)viewDidLoad {
    [super viewDidLoad];
    Person * p = [[Person alloc]init];
    p.name = @"ldd";
    p.age = @"26";
    p.height = @"1.80";
    NSString * filePath = [@"/Users/fangduozhang/Desktop" stringByAppendingPathComponent:@"LDD.data"];
    [NSKeyedArchiver archiveRootObject:p toFile:filePath];
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    Person * p = [NSKeyedUnarchiver unarchiveObjectWithFile:[@"/Users/fangduozhang/Desktop" stringByAppendingPathComponent:@"LDD.data"]];
    NSLog(@"%@---%@---%@",p.name,p.age,p.height);
}

八.数据库动态方案

https://github.com/Buliceli/LDnamicDataBase

鉴于能力有限水平一般理解有误之处望大侠不吝指出 ThankYou!

Runtime学习笔记

一.消息机制

二.交换方法

三.动态添加方法

四.动态添加属性

五.字典转模型

六.KVO的底层实现

七.归档&解档

八.数据库动态方案

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