1 | // Copyright 2017-2022 @polkadot/types authors & contributors
|
2 | // SPDX-License-Identifier: Apache-2.0
|
3 |
|
4 | /**
|
5 | * @name lazyMethod
|
6 | * @description
|
7 | * Creates a lazy, on-demand getter for the specific value. Upon get the value will be evaluated.
|
8 | */
|
9 | export function lazyMethod(result, item, creator, getName) {
|
10 | const name = getName ? getName(item) : item.toString();
|
11 | let value;
|
12 | Object.defineProperty(result, name, {
|
13 | // This allows for re-configuration with the embedded defineProperty below
|
14 | // and ensures that on tested browsers and Node, it _will_ be redefined
|
15 | // and thus short-circuited for future access
|
16 | configurable: true,
|
17 | enumerable: true,
|
18 | // Use a function here, we don't want to capture the outer this, i.e.
|
19 | // don't use arrow functions in this context since we have a this inside
|
20 | get: function () {
|
21 | // This check should _always_ be false and unneeded, since we override
|
22 | // with a value below ... however we ensure we are quire vigilant against
|
23 | // all environment failures, so we are rather be safe than sorry
|
24 | if (value === undefined) {
|
25 | value = creator(item);
|
26 |
|
27 | try {
|
28 | // re-define the property as a value, next time around this
|
29 | // getter will only return the computed value
|
30 | Object.defineProperty(this, name, {
|
31 | value
|
32 | });
|
33 | } catch {// ignore any errors, since this _should_ not happen due to
|
34 | // the "configurable" property above. But if it ever does
|
35 | // from here-on we will be the cached value the next time
|
36 | // around (with a very slight dip in performance)
|
37 | }
|
38 | }
|
39 |
|
40 | return value;
|
41 | }
|
42 | });
|
43 | }
|
44 | /**
|
45 | * @name lazyMethods
|
46 | * @description
|
47 | * Creates lazy, on-demand getters for the specific values.
|
48 | */
|
49 |
|
50 | export function lazyMethods(result, items, creator, getName) {
|
51 | for (let i = 0; i < items.length; i++) {
|
52 | lazyMethod(result, items[i], creator, getName);
|
53 | }
|
54 |
|
55 | return result;
|
56 | } |
\ | No newline at end of file |