GCD，Block和动态加载混合

来源：互联网发布：人工智能服务器编辑：程序博客网时间：2024/05/20 18:00

GCD，Block和动态加载混合

由于这几天分析了SDWebImage和AFNetWorking，了解到GCD和Block的好处，于是今天尝试把原来项目食趣的代码利用GCD，Block和动态加载改了，那么问题来了。

场景解析：

1.消费记录页面需要两个接口去服务器请求数据

2.加载成功和失败共有一个小菊花View

问题1:

使用dispatch_group_async：

_queue=dispatch_queue_create("getData", DISPATCH_QUEUE_SERIAL);

_group = dispatch_group_create();

dispatch_group_async(self.group, self.queue,^{

//获取price

//动态加载

__block SEL sel =NSSelectorFromString(@"getPrice");

if ([self respondsToSelector: sel])SuppressPerformSelectorLeakWarning([self performSelector: sel withObject:nil]);

});

dispatch_group_async(self.group, self.queue,^{

//获取order

__block SEL sel =NSSelectorFromString(@"getOrder");

if ([selfrespondsToSelector: sel]) SuppressPerformSelectorLeakWarning([selfperformSelector:sel withObject: nil]);

});

dispatch_group_notify(self.group,self.queue, ^{

//更新UI

NSLog(@"%@",self.recordOfConsumptionArray);

// [self.recordOfConsumptionTableView reloadData];

});

A:不管怎么处理，第一次网络请求是没有数据的NSLog(@"%@",self.recordOfConsumptionArray);

打印为空。

于是把queue改成_queue =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);可是结果还是一样。

本来多个数据请求使用dispatch_group_async是一个非常好的方法选择，可是问题来了，加载成功和失败共有一个小菊花View，使用异步小菊花不知道怎么释放了，以及dispatch_group_notify里面的block回调不到数据。

B:这个问题的解决根源还是要靠线程管理

使用：dispatch_queue_create("getData",DISPATCH_QUEUE_SERIAL)和dispatch_sync，

通过debug数据程序跟踪，完美的解决

dispatch_sync(self.queue, ^{

//获取price

//动态加载

__block SEL sel = NSSelectorFromString(@"getPrice");

if ([self respondsToSelector: sel])SuppressPerformSelectorLeakWarning([self performSelector: selwithObject: nil]);

});

dispatch_sync(self.queue, ^{

//获取order

__block SEL sel = NSSelectorFromString(@"getOrder");

if ([self respondsToSelector: sel])SuppressPerformSelectorLeakWarning([self performSelector:selwithObject: nil]);

});

可是问题还有一个就是AFNetWorking的success: failure:回调方法，这可能是数据一时还没有获取到，因为线程分之了，马上执行了dispatch_group_notify的block，可是数据的获取还在success：回调方法里面，由于并发的原因，导致了在[weakSelf.recordOfConsumptionTableViewreloadData];更新数据的时间点，数据还没有到，只因为它们不在一条线程以及一个队里面。

当然我试过：

dispatch_sync(self.queue, ^{

//获取price

//动态加载

__block SEL sel = NSSelectorFromString(@"getPrice");

if ([self respondsToSelector: sel])SuppressPerformSelectorLeakWarning([self performSelector: selwithObject: nil]);

});

dispatch_barrier_async(dispatch_get_main_queue(), ^{

//获取order

__block SEL sel = NSSelectorFromString(@"getOrder");

if ([self respondsToSelector: sel])SuppressPerformSelectorLeakWarning([selfperformSelector:selwithObject: nil]);

});

dispatch_barrier_async(self.queue, ^{

NSLog(@"%@", self.recordOfConsumptionArray);

[self.recordOfConsumptionTableView reloadData];

});

可是还是解决不了。问题的根源就是共有一个view，这个view的状态更改不能在子线程里面处理。

问题2:

动态加载：performSelector may cause a leak becauseits selector is unknown"警告

http://www.tuicool.com/articles/iu6zuu ios之"performSelector may cause a leak because itsselector is unknown"警告原因及其解决办法

// 使用宏忽略警告 performSelector may causea leak because its selector is unknown"警告原因及其解决办法

#defineSuppressPerformSelectorLeakWarning(Stuff) \

do { \

_Pragma("clang diagnosticpush")\

_Pragma("clang diagnosticignored \"-Warc-performSelector-leaks\"") \

Stuff; \

_Pragma("clang diagnosticpop")\

} while (0)

//动态加载

__block SEL sel = NSSelectorFromString(@"getPrice");

if ([self respondsToSelector: sel])SuppressPerformSelectorLeakWarning([self performSelector: selwithObject: nil]);

原因

在ARC模式下，运行时需要知道如何处理你正在调用的方法的返回值。这个返回值可以是任意值，如 void , int , char , NSString , id 等等。ARC通过头文件的函数定义来得到这些信息。所以平时我们用到的静态选择器就不会出现这个警告。因为在编译期间，这些信息都已经确定。

问题3:

capturing 'self' strongly in this block is likely to lead a retain cycle

为了封装方法和使用block回调：

typedef void (^getURLBlock)(NSDictionary *dic);

@property (nonatomic, copy) getURLBlock urlBlock;

- (NSDictionary *)getURLData: (NSString *)url parameters:(NSDictionary *)parameters

{

__weak __typeof(self)weakSelf = self;

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

[manager POST: url parameters: parameters success: ^(AFHTTPRequestOperation *operation, id successObject){

__weak NSData *data =operation.responseData;

__weak NSDictionary *dic = [NSJSONSerializationJSONObjectWithData: data options:NSJSONReadingMutableContainers error: nil];

weakSelf.urlBlock(dic);

}failure: ^(AFHTTPRequestOperation *operation, NSError *error){

[weakSelf makeToast: ERR_NETWORK];

[DejalBezelActivityView removeViewAnimated: YES];

[weakSelf.pullToRefreshtableViewReloadFinishedAnimated:YES];

}];

return [NSDictionary dictionary];

}

//请求price

- (void)getPrice

{

__weak NSDictionary *dic = [CommonUtil getObjectFromUD:@"userInfo"];

if([CommonUtil isEmpty:dic[@"user_id"]]){

return;

}

__weak NSString *url = [RequestHelpergetFullUrl:@"/api/user/myorder" Host:REQUEST_HOST];

__weak NSDictionary *parameters = [NSDictionarydictionaryWithObjectsAndKeys: dic[@"user_id"], @"user_id", nil];

[DejalBezelActivityView activityViewForView: self.view];

__block SEL sel =NSSelectorFromString(@"getURLData:parameters:");

if ([self respondsToSelector: sel])SuppressPerformSelectorLeakWarning([self performSelector: selwithObject: url withObject: parameters]);

//解决循环引用的bug capturing 'self'strongly in this block is likely to lead a retain cycle

__weak __typeof(self)weakSelf = self;

self.urlBlock = ^(NSDictionary *dic){

NSInteger code = [[dic objectForKey: @"code"]integerValue];

if (code == 1) {

//操作成功

//循环引用的bug

// self.total_priceLabel.text =[NSString stringWithFormat: @"%0.2f", [[dic objectForKey:@"total"] doubleValue]];

// self.save_priceLabel.text =[NSString stringWithFormat: @"%0.2f", [[dic objectForKey:@"save"] doubleValue]];

weakSelf.total_priceLabel.text = [NSStringstringWithFormat: @"%0.2f", [[dic objectForKey: @"total"]doubleValue]];

weakSelf.save_priceLabel.text = [NSStringstringWithFormat: @"%0.2f", [[dic objectForKey: @"save"]doubleValue]];

}else{

[weakSelf makeToast: [dic objectForKey: @"message"]];

[DejalBezelActivityView removeViewAnimated: YES];

}

};

可是问题又来了：多个网络请求，block回调方法出不去就异步请求了，这回到的上面的问题了；没办法只有再来一个block

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