尝试将
HTML从Web服务加载到webview中,我收到此错误：
Reference to property ‘webviewHTML’ in closure requires explicit ‘self.’ to make capture semantics explicit
它是什么意思,我如何将HTML字符串加载到我的Web视图中？
func post(url: String,params: String) {
let url = NSURL(string: url)
let params = String(params);
let request = NSMutableURLRequest(URL: url!);
request.HTTPMethod = "POST"
request.HTTPBody = params.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data,response,error in
if error != nil {
print("error=\(error)")
return
}
var responseString : NSString!;
responseString = NSString(data: data!,encoding: NSUTF8StringEncoding)
webviewHTML.loadHTMLString(String(responseString),baseURL: nil)
}
task.resume();
}
在回答这个问题之前,你必须知道记忆周期是什么.见
Resolving Strong Reference Cycles Between Class Instances From Apple’s documenation
原文链接：https://www.f2er.com/swift/319249.html现在你知道什么是内存周期了：
那个错误是Swift编译器告诉你的
“Hey the NSURLSession closure is trying to keep webviewHTML in
the heap and therefor self ==> creating a memory cycle and I don’t
think Mr.Clark wants that here. Imagine if we make a request which takes
forever and then the user navigates away from this page. It won’t
leave the heap.I’m only telling you this,yet you Mr.Clark must create a weak reference to the self and use that in the closure.”
我们使用[弱自我]创建(即capture)弱引用.我强烈建议您查看附加链接的捕获方式.
欲了解更多信息,请参阅斯坦福大学课程this moment.
正确的代码
func post(url: String,params: String) {
let url = NSURL(string: url)
let params = String(params);
let request = NSMutableURLRequest(URL: url!);
request.HTTPMethod = "POST"
request.HTTPBody = params.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
[weak weakSelf self] data,encoding: NSUTF8StringEncoding)
weakSelf?.webviewHTML.loadHTMLString(String(responseString),baseURL: nil)
// USED `weakSelf?` INSTEAD OF `self`
}
task.resume();
}
有关详细信息,请参阅此Shall we always use [unowned self] inside closure in Swift
