The Tor Browser / file comparison
comparison: addon-sdk/source/lib/sdk/util/dispatcher.js
addon-sdk/source/lib/sdk/util/dispatcher.js
- branch
- TOR_BUG_3246
- changeset 7
- 129ffea94266
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| -1:000000000000 | 0:954b507412d0 |
|---|---|
| 1 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 2 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. | |
| 4 */ | |
| 5 "use strict"; | |
| 6 | |
| 7 module.metadata = { | |
| 8 "stability": "experimental" | |
| 9 }; | |
| 10 | |
| 11 const method = require("method/core"); | |
| 12 | |
| 13 // Utility function that is just an enhancement over `method` to | |
| 14 // allow predicate based dispatch in addition to polymorphic | |
| 15 // dispatch. Unfortunately polymorphic dispatch does not quite | |
| 16 // cuts it in the world of XPCOM where no types / classes exist | |
| 17 // and all the XUL nodes share same type / prototype. | |
| 18 // Probably this is more generic and belongs some place else, but | |
| 19 // we can move it later once this will be relevant. | |
| 20 let dispatcher = hint => { | |
| 21 const base = method(hint); | |
| 22 // Make a map for storing predicate, implementation mappings. | |
| 23 let implementations = new Map(); | |
| 24 | |
| 25 // Dispatcher function goes through `predicate, implementation` | |
| 26 // pairs to find predicate that matches first argument and | |
| 27 // returns application of arguments on the associated | |
| 28 // `implementation`. If no matching predicate is found delegates | |
| 29 // to a `base` polymorphic function. | |
| 30 let dispatch = (value, ...rest) => { | |
| 31 for (let [predicate, implementation] of implementations) { | |
| 32 if (predicate(value)) | |
| 33 return implementation(value, ...rest); | |
| 34 } | |
| 35 | |
| 36 return base(value, ...rest); | |
| 37 }; | |
| 38 | |
| 39 // Expose base API. | |
| 40 dispatch.define = base.define; | |
| 41 dispatch.implement = base.implement; | |
| 42 dispatch.toString = base.toString; | |
| 43 | |
| 44 // Add a `when` function to allow extending function via | |
| 45 // predicates. | |
| 46 dispatch.when = (predicate, implementation) => { | |
| 47 if (implementations.has(predicate)) | |
| 48 throw TypeError("Already implemented for the given predicate"); | |
| 49 implementations.set(predicate, implementation); | |
| 50 }; | |
| 51 | |
| 52 return dispatch; | |
| 53 }; | |
| 54 | |
| 55 exports.dispatcher = dispatcher; |
