while(condition){Object.wait()}成语(while(condition) { Object.wait() } idiom)
我知道,我们使用这个成语来等待通知来处理虚假唤醒:
synchronized (obj) { while(somecond) obj.wait(); }
如果出现虚假唤醒,我们只需检查状态并返回等待状态。
但是,考虑一下情况:
- 我们开始等待,obj.wait()释放对obj的锁定。
- 等待线程被操作系统虚假通知
- 我们返回到检查状态(由于等待而释放对象锁)
- obj.notify()在那一刻被调用。
是的,条件检查速度非常快,而且我们可以进行条件检查,而不是在
obj.wait()
,这些检查的obj.wait()
很小,可以忽略不计。 在这种情况下,我们可以obj.notify()
调用。我误解了什么,或者我们真的可以使用这种模式发布通知?
I know, that we use this idiom for waiting for notification to handle spurious wakeups:
synchronized (obj) { while(somecond) obj.wait(); }
If a spurious wake up arises, we'll just check the state and return back to waiting.
But, consider the situation:
- We begin waiting, and obj.wait() releases lock on obj.
- Waiting thread is spuriously notified by OS
- We return to checking condition (with obj lock released due to wait)
- obj.notify() is called right in that moment.
Yes, condition checking is extremely fast and chances, that we can be in condition checking and not in
obj.wait()
, are negligibly small. In that case we can looseobj.notify()
call.Am I misunderstanding something, or we really can loose notification using this pattern?
原文:https://stackoverflow.com/questions/21721401
最满意答案
当我最初试图让Bootstrap popovers工作时,我(当然,仍然有)很多缺失的上下文理解。
首先是:Bootstrap“Popover”插件实际上是一个JQuery插件 。 我假设所有的Bootstrap插件都是如何工作的,但我找不到任何关于这个的Bootstrap介绍性文档。 这就解释了
popover()
方法及其来源。下面,我概述了使弹出窗口在React / Typescript / Webpack堆栈的上下文中工作所需的内容。
在下面,我假设你按照Bootstrap doco配置了Webpack。
您不需要原始问题中的“Popover”和“Tooltip”行,假设您的
webpack.config.js
是按照Bootstrap doco并且您已import 'bootstrap';
代码库中的某个地方。
您需要添加JQuery类型(如果尚未存在),以便您可以导入
$
并使用正确的类型:"devDependencies": { "@types/jquery": "3.2.15", ... } "dependencies": { "bootstrap": "4.0.0-beta", "jquery": "3.2.1", "popper.js": "1.11.0", ... }
根据Netanel Basal的博客文章,您必须扩展JQuery的类型定义,以便它了解Popover插件。 在
typings.d.ts
(或项目中的任何地方),添加以下内容:// support for JQuery popover plugin from Bootstrap 4 interface JQuery { popover() : any; }
请注意,定义是您以极其静态方式从代码中获取弹出窗口所需的最低限度。 需要扩展它以支持传递参数,以便您可以自定义弹出行为。 或者您可以使用
data
属性来传递这些参数,如doco中的Live示例所示 。在React组件本身中,从问题中声明popover的JSX似乎工作正常。
要根据问题“初始化”弹出窗口,您需要导入JQuery标识符,然后调用popover方法:
... const $ = require('jquery'); ... componentDidMount(): void{ $('[data-toggle="popover"]').popover(); } ...
“导入表单” 对我不起作用 ,所以我不得不
require()
它。该代码在整个HTML页面中搜索带有
data-toggle="popover"
元素,并返回一个JQuery对象,该对象具有可以调用的popover()
方法(这是整个JQuery插件部分)。一旦在具有弹出属性的元素上调用了popover
popover()
,单击该元素时将自动显示弹出窗口(不需要管理特定于弹出窗口的React状态)。
编辑
如上所示,在整个HTML页面中搜索所有弹出窗口并不是一个好主意。 在一个复杂的页面中,在多个React组件中有多个
popover()
,每个组件最终会覆盖彼此的popover()
选项。这是我目前可重用的React bootstrap Popover组件的解决方案。
扩展Typescript类型以了解更多popover 选项 :
// support for JQuery popover plugin from Bootstrap 4 interface JQuery { popover(options?: PopoverOptions) : any; } interface PopoverOptions { container?: string | Element | boolean; content?: string | Element | Function; placement?: "auto" | "top" | "bottom" | "left" | "right" | Function; title?: string | Element | Function; ... }
像
Popover.tsx
这样创建Popover.tsx
:export interface PopoverProps { popoverTitle: string | Element | Function; popoverContent: string | Element | Function; } export class Popover extends PureComponent<PopoverProps, object> { selfRef: HTMLSpanElement; componentDidMount(): void{ $(this.selfRef).popover({ container: this.selfRef, placement: "auto", title: this.props.popoverTitle, content: this.props.popoverContent, }); } render(){ return <span ref={(ref)=>{if(ref) this.selfRef = ref}} data-toggle="popover" > {this.props.children} </span>; } }
然后使用popover像:
<Popover popoverTitle="The popover title" popoverContent="The popover content" > <span> Click this to show popover. </span> </Popover>
注意与使用动态内容的Popover定位相关的问题: Bootstrap 4 - 自动Popover重新定位如何工作?
I had (still have, undoubtedly) a lot of missing contextual understanding when I was initially trying to get Bootstrap popovers working.
First thing is: the Bootstrap "Popover" plugin is really a JQuery plugin. I assume that's how all the Bootstrap plugins work, but I couldn't find any Bootstrap introductory documentation about this. So that explains the
popover()
method and where it comes from.Below, I've outlined what is needed to make the popovers work in the context of a React / Typescript / Webpack stack.
In the following, I'm assuming you've configured Webpack as per the Bootstrap doco.
You don't need the "Popover" and "Tooltip" lines from the original question, assuming you're
webpack.config.js
is as per the Bootstrap doco and you haveimport 'bootstrap';
somewhere in your codebase.
You need to add the JQuery typings, if not already present, so that you can import
$
and have the right types:"devDependencies": { "@types/jquery": "3.2.15", ... } "dependencies": { "bootstrap": "4.0.0-beta", "jquery": "3.2.1", "popper.js": "1.11.0", ... }
You have to extend the type definition of JQuery so that it knows about the Popover plugin, as per this blog article by Netanel Basal. In
typings.d.ts
(or wherever makes sense in your project), add the following:// support for JQuery popover plugin from Bootstrap 4 interface JQuery { popover() : any; }
Note that definition is the bare minimum you need to get popovers working from your code in a statically typed way. It needs to be extended to support passing parameters so that you can customise the popover behaviour. Or you could use the
data
attributes to pass these parameters, as per the Live example in the doco.In the React component itself, the JSX to declare the popover from the question seems to work fine.
To "initialize" the popover, as per the question, you need to import the JQuery identifier and then call the popover method:
... const $ = require('jquery'); ... componentDidMount(): void{ $('[data-toggle="popover"]').popover(); } ...
The "import form" didn't work for me, so I had to
require()
it.That code searches the entire HTML page for elements with
data-toggle="popover"
, and returns a JQuery object that has thepopover()
method you can call (that's the whole JQuery plugin part).Once
popover()
has been called on the element with the popover attributes, popovers will be automatically displayed when the element is clicked (there's no need to manage popover-specific React state).
EDIT
It's not a good idea to search the entire HTML page for all popovers as shown above. In a complicated page with multiple popovers in multiple React components, each component would end up overwriting each other's
popover()
options.Here's my current solution for a re-usable React bootstrap Popover component.
Extend the Typescript typings to understand more popover options:
// support for JQuery popover plugin from Bootstrap 4 interface JQuery { popover(options?: PopoverOptions) : any; } interface PopoverOptions { container?: string | Element | boolean; content?: string | Element | Function; placement?: "auto" | "top" | "bottom" | "left" | "right" | Function; title?: string | Element | Function; ... }
Create
Popover.tsx
like:export interface PopoverProps { popoverTitle: string | Element | Function; popoverContent: string | Element | Function; } export class Popover extends PureComponent<PopoverProps, object> { selfRef: HTMLSpanElement; componentDidMount(): void{ $(this.selfRef).popover({ container: this.selfRef, placement: "auto", title: this.props.popoverTitle, content: this.props.popoverContent, }); } render(){ return <span ref={(ref)=>{if(ref) this.selfRef = ref}} data-toggle="popover" > {this.props.children} </span>; } }
Then use the popover like:
<Popover popoverTitle="The popover title" popoverContent="The popover content" > <span> Click this to show popover. </span> </Popover>
Beware issues related to Popover positioning with dynamic content: Bootstrap 4 - how does automatic Popover re-positioning work?
相关问答
更多-
基于我在我的bootstrap.css文件中,默认是一个max-width属性。 我用这个 .popover { position: absolute; top: 0; left: 0; z-index: 1010; display: none; max-width: 600px; padding: 1px; text-align: left; white-space: normal; background-color: #ffffff; border: 1px ...
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如何在React应用程序中初始化Bootstrap 4 popover?(How do I initialize the Bootstrap 4 popover in a React application?)[2023-02-10]
当我最初试图让Bootstrap popovers工作时,我(当然,仍然有)很多缺失的上下文理解。 首先是:Bootstrap“Popover”插件实际上是一个JQuery插件 。 我假设所有的Bootstrap插件都是如何工作的,但我找不到任何关于这个的Bootstrap介绍性文档。 这就解释了popover()方法及其来源。 下面,我概述了使弹出窗口在React / Typescript / Webpack堆栈的上下文中工作所需的内容。 在下面,我假设你按照Bootstrap doco配置了Webpac ...与bootstrap 3选择不正常相似, 所选行为需要在内容准备好后初始化。 与模态事件类似,您可以使用popover事件: $('#thing').popover( // content, title, etc... ).on('shown.bs.popover', function () { $('.chosen-select').chosen(); }).on('hidden.bs.popover', function () { // Destroy when the popover is ...我想出了解决方案。 制作popover时,bootstrap会在父容器中生成div元素。 显然,当它在svg里面时,它不能正常工作。 所以这里是解决方案,给它一个data-container集作为body你也可以去掉一个元素,然后直接将它添加到circle元素。相关文章
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