76 lines
2.1 KiB
Markdown
76 lines
2.1 KiB
Markdown
# ipc (main process)
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The `ipc` module, when used in the main process, handles asynchronous and
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synchronous messages sent from a renderer process (web page). Messages sent from
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a renderer will be emitted to this module.
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## Sending Messages
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It is also possible to send messages from the main process to the renderer
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process, see [WebContents.send](browser-window.md#webcontentssendchannel-args)
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for more information.
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- When sending a message, the event name is the `channel`.
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- To reply a synchronous message, you need to set `event.returnValue`.
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- To send an asynchronous back to the sender, you can use
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`event.sender.send(...)`.
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An example of sending and handling messages between the render and main
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processes:
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```javascript
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// In main process.
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var ipc = require('ipc');
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ipc.on('asynchronous-message', function(event, arg) {
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console.log(arg); // prints "ping"
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event.sender.send('asynchronous-reply', 'pong');
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});
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ipc.on('synchronous-message', function(event, arg) {
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console.log(arg); // prints "ping"
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event.returnValue = 'pong';
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});
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```
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```javascript
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// In renderer process (web page).
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var ipc = require('ipc');
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console.log(ipc.sendSync('synchronous-message', 'ping')); // prints "pong"
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ipc.on('asynchronous-reply', function(arg) {
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console.log(arg); // prints "pong"
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});
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ipc.send('asynchronous-message', 'ping');
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```
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## Listening for Messages
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The `ipc` module has the following method to listen for events:
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### `ipc.on(channel, callback)`
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* `channel` String - The event name.
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* `callback` Function
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When the event occurs the `callback` is called with an `event` object and a
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message, `arg`.
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## IPC Events
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The `event` object passed to the `callback` has the following methods:
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### `Event.returnValue`
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Set this to the value to be returned in a synchronous message.
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### `Event.sender`
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Returns the `WebContents` that sent the message.
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### `Event.sender.send(channel[, arg1][, arg2][, ...])`
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* `channel` String - The event name.
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* `arg` (optional)
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This sends an asynchronous message back to the render process. Optionally, there
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can be one or a series of arguments, `arg`, which can have any type.
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