-
-
Save wulucxy/2abcd18f3a04cae26a355b071e375efd to your computer and use it in GitHub Desktop.
#dbc #契约式设计
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| // 示例来源：https://qiita.com/Jxck_/items/defd80843a4beb5fcfc8 | |
| # 定义公共的契约调用规则 | |
| function contract(rule) { | |
| return function(target, name, descriptor) { | |
| let rule = new Rule(target, name, descriptor); | |
| let original = descriptor.value; | |
| descriptor.value = function() { | |
| if (rule.before) rule.before.apply(rule, arguments); | |
| if (rule.invaliant) rule.invaliant(this); | |
| let result = original.apply(this, arguments); | |
| if (rule.invaliant) rule.invaliant(this); | |
| if (rule.after) rule.after(result); | |
| return result; | |
| } | |
| } | |
| } | |
| # 具体规则 | |
| class Rule { | |
| constructor(target, name, descriptor) { | |
| this.target = target; | |
| this.name = name; | |
| this.descriptor = descriptor; | |
| } | |
| // 前置条件 | |
| before(i) { | |
| console.log('before', i); | |
| console.assert(i > 0, `arg for ${this.name} should be positive value`); | |
| } | |
| // 后置条件 | |
| after(result) { | |
| console.log('after', result); | |
| console.assert(result > 0, `result of ${this.name} should be positive value`); | |
| } | |
| // 不可变式 | |
| invaliant(_this) { | |
| console.log('invaliant', _this); | |
| console.assert(_this.current > 0, '`current` should be positive value'); | |
| } | |
| } | |
| function main() { | |
| class Counter { | |
| constructor(initial = 0) { | |
| this.current = initial; | |
| } | |
| @contract(Rule) | |
| up(i) { | |
| this.current += i; | |
| return this.current; | |
| } | |
| } | |
| let counter = new Counter(10); | |
| console.log(counter.up(2)); | |
| } | |
| main(); |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment