javascript - 在 Bootstrap 插件中卸载惰性 setter/getter ？

Question

在我的 bootstrap.js 顶部，我定义了一堆 lazyGetter，而不是 JSM:

const myServices = {};
Cu.import('resource://gre/modules/XPCOMUtils.jsm');
XPCOMUtils.defineLazyGetter(myServices, 'sss', function(){ return Cc['@mozilla.org/content/style-sheet-service;1'].getService(Ci.nsIStyleSheetService) });

我听说您必须卸载 导入的模块。但是你为 lazyGetter 创建的“模块”呢？我将如何卸载那些？我会做一个 delete myServices 吗？

如果我对全局变量 myServices 执行delete，是否意味着我应该在卸载时删除所有全局变量？

我在这里阅读:Forgetting to unload JavaScript modules in restartless add-ons

Forgetting to unload JavaScript modules in restartless add-ons

Another common cause of leaks is forgetting to unload JavaScript code modules in bootstrapped add-ons. These leaks cannot be detected by looking at about:compartments or about:memory because such modules live within the main System compartment.

Also, when your add-on gets updated and re-enabled, the previous module version that is still loaded will be used, which might break your add-on entirely.

The following example shows how to unload your modules again (bootstrap.js):

Components.utils.import("resource://gre/modules/Services.jsm");

function startup(data, reason) {
  // This assumes your add-on did register some chrome
  Components.utils.import("chrome://myaddon/content/mymodule.jsm");
}

function shutdown(data, reason) {
  if (reason != APP_SHUTDOWN) {
    // No need to do regular clean up when the application is closed
    // unless you need to break circular references that might negatively
    // impact the shutdown process.
    return;
  }

  // Your add-on needs to unload all modules it ships and imported!
  Components.utils.unload("chrome://myaddon/content/mymodule.jsm");
}

Note: Modules not belonging to your add-on — such as Services.jsm — should not be unloaded by your add-on, as this might cause errors and/or performance regressions and will actually increase the memoryusage.

Answer 1

你提供的代码没有引入模块，只是定义了一个service getter，所以没问题。

(旁白:还有一个 XPCOMUtils.defineLazyServiceGetter helper ...)

但是如果你做了这样的事情:

XPCOMUtils.defineLazyGetter(myServices, 'SomeSymbol', function() {
   return Cu.import("chrome://myaddon/content/mymodule.jsm", {}).SomeSymbol;
});

那么您当然需要再次Cu.unload() 那个模块。最好通过注册模块在加载后立即卸载来完成(IMO)，例如:

XPCOMUtils.defineLazyGetter(myServices, 'SomeSymbol', function() {
   let rv = Cu.import("chrome://myaddon/content/mymodule.jsm", {}).SomeSymbol;
   unload(function() {
     Cu.unload("chrome://myaddon/content/mymodule.jsm");
   });
   return rv;
});

其他人只是主动卸载所有可能已导入或未导入的模块。这很好，因为 Cu.unload() 加载未导入的模块什么都不做。

PS:将某些东西插入另一个模块时，您仍然会遇到麻烦，例如。

XPCOMUtils.defineLazyServiceGetter(Services /* other module */,
                                   'sss',
                                   '@mozilla.org/content/style-sheet-service;1',
                                   'nsIStyleSheetService');

在此示例中，XPCOMUtils.jsm 可能仍会引用作为参数从您的代码中传递的字符串，从而泄漏您的代码。 (此外，将内容粘贴到不属于您自己的模块中是相当粗鲁的，并且可能会与其他执行相同操作的附加组件发生冲突。)