class WeakPtrFactory

Class that produces (valid) |WeakPtr

<T

>|s. Typically, this is used as a

member variable of |T| (preferably the last one -- see below), and |T|'s

methods control how weak pointers to it are vended. This class is not

thread-safe, and should only be used on a single thread.

Example:

class Controller {

public:

Controller() : ..., weak_factory_(this) {}

...

void SpawnWorker() { Worker::StartNew(weak_factory_.GetWeakPtr()); }

void WorkComplete(const Result

&

result) { ... }

private:

...

// Member variables should appear before the |WeakPtrFactory|, to ensure

// that any |WeakPtr|s to |Controller| are invalidated before its member

// variables' destructors are executed.

WeakPtrFactory

<Controller

> weak_factory_;

};

class Worker {

public:

static void StartNew(const WeakPtr

<Controller

>

&

controller) {

Worker* worker = new Worker(controller);

// Kick off asynchronous processing....

}

private:

Worker(const WeakPtr

<Controller

>

&

controller) : controller_(controller) {}

void DidCompleteAsynchronousProcessing(const Result

&

result) {

if (controller_)

controller_->WorkComplete(result);

}

WeakPtr

<Controller

> controller_;

};