PSA: WTF::Function is gone, but you should still use WTF::Bind or WTF::BindRepeating

[Yuta Kitamura]

Hi all,

As part of our cleanup effort, WTF::Function is now gone; WTF::Bind() now directly returns base::OnceCallback.

WTF::Bind() still exists, though, and you actually still need to keep using it. Unlike base::Bind(), WTF::Bind() does some static type checking on Oilpan types, and it also adds code that checks threading usage on debug builds. Currently, there's no plan to deprecate WTF::Bind().

Also, a new variant of WTF::Bind() has been introduced: WTF::BindRepeating(). This creates base::RepeatingCallback, which is for callbacks that may be called multiple times.

For cross-thread callbacks, nothing has changed: use blink::CrossThreadBind() (defined in platform/CrossThreadFunctional.h). It returns WTF::CrossThreadFunction, and this will not change soon.

To sum up:

• To create a cross-thread callback: use blink::CrossThreadBind(), which returns WTF::CrossThreadFunction.
• To create a single-threaded callback that's called only once: use WTF::Bind(), which returns base::OnceCallback.
• To create a single-threaded callback that may be called many times: use WTF::BindRepeating(), which returns base::RepeatingCallback.

For details, see the comments in Functional.h.

Thanks,

Yuta

[Kentaro Hara]

Excellent! \o/

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Kentaro Hara, Tokyo, Japan

[Hiroki Nakagawa]

Nice! Do you have a plan to rename WTF::Bind to WTF::BindOnce for consistency with base::BindOnce? I'm just curious.

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[Yuta Kitamura]

I heard //base's plan was to have base::Bind (for once) and base::BindRepeating and remove base::BindOnce in the end. So actually WTF's current setup matches //base's final state.

2017/12/15 20:52 "Hiroki Nakagawa" <nhi...@chromium.org>:

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[Hiroki Nakagawa]

Thanks! I didn't know it :)