iOS runtime 关联对象（Associated Object）
需求
同一个类有多个alertView, 不同的alertView 点击确定按钮 执行的方法不同
alertOne 点击 确定按钮 执行 methodOne， alertTwo 点击确定按钮 执行 methodTwo
常规做法
初始化并显示 alertOne
- (IBAction)showAlertOne:(id)sender {
UIAlertView *alertOne = [[UIAlertView alloc]initWithTitle:@"AlertOne" message:@"" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
[alertOne setTag:1];
[alertOne show];
}
初始化并显示alertTwo
- (IBAction)showAlertTwo:(id)sender {
UIAlertView *alertTwo = [[UIAlertView alloc]initWithTitle:@"AlertTwo" message:@"" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
[alertTwo setTag:2];
[alertTwo show];
}
实现代理
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
if (buttonIndex == 0) {
return;
}
if (alertView.tag == 1) {
if (buttonIndex == 1) {
[self methodOne];
}
}
else if (alertView.tag == 2) {
if (buttonIndex == 1) {
[self methodTwo];
}
}
}
Associated Object 做法
import runtime.h，定义属性关联key
#import "ViewController.h" #import <objc/runtime.h> static void *alertViewKey = "alertViewKey";
初始化并显示 alertOne，同时定义block，将block 与 alertOne 关联
- (IBAction)showAlertOne:(id)sender {
UIAlertView *alertOne = [[UIAlertView alloc]initWithTitle:@"AlertOne" message:@"" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
void (^block)(NSInteger) = ^(NSInteger buttonIndex) {
if (buttonIndex == 1) {
[self methodOne];
}
};
objc_setAssociatedObject(alertOne, alertViewKey, block, OBJC_ASSOCIATION_COPY);//将block 与 alertOne 关联
[alertOne show];
初始化并显示 alertTwo，同时定义block，将block 与 alertTwo 关联
- (IBAction)showAlertTwo:(id)sender {
UIAlertView *alertTwo = [[UIAlertView alloc]initWithTitle:@"AlertTwo" message:@"" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
void (^block)(NSInteger) = ^(NSInteger buttonIndex) {
if (buttonIndex == 1) {
[self methodTwo];
}
};
objc_setAssociatedObject(alertTwo, alertViewKey, block, OBJC_ASSOCIATION_COPY);
[alertTwo show];
}
实现代理，在代理方法中，直接取出当前alert 所关联上的 block，再将buttonIndex 传入，让block 自己调用对应方法
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
if (buttonIndex == 0) {
return;
}
void(^block)(NSInteger) = objc_getAssociatedObject(alertView, alertViewKey);
block(buttonIndex);
}
比较
通过使用Associated object 方法有多个好处 ：
简化代码
让代码层次清晰
充分利用对象与属性的拥有关系