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158 lines
3.9 KiB
Markdown
158 lines
3.9 KiB
Markdown
Chainsaw
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========
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Build chainable fluent interfaces the easy way in node.js.
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With this meta-module you can write modules with chainable interfaces.
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Chainsaw takes care of all of the boring details and makes nested flow control
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super simple too.
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Just call `Chainsaw` with a constructor function like in the examples below.
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In your methods, just do `saw.next()` to move along to the next event and
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`saw.nest()` to create a nested chain.
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Examples
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========
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add_do.js
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---------
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This silly example adds values with a chainsaw.
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var Chainsaw = require('chainsaw');
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function AddDo (sum) {
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return Chainsaw(function (saw) {
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this.add = function (n) {
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sum += n;
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saw.next();
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};
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this.do = function (cb) {
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saw.nest(cb, sum);
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};
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});
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}
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AddDo(0)
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.add(5)
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.add(10)
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.do(function (sum) {
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if (sum > 12) this.add(-10);
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})
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.do(function (sum) {
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console.log('Sum: ' + sum);
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})
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;
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Output:
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Sum: 5
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prompt.js
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---------
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This example provides a wrapper on top of stdin with the help of
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[node-lazy](https://github.com/pkrumins/node-lazy) for line-processing.
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var Chainsaw = require('chainsaw');
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var Lazy = require('lazy');
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module.exports = Prompt;
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function Prompt (stream) {
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var waiting = [];
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var lines = [];
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var lazy = Lazy(stream).lines.map(String)
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.forEach(function (line) {
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if (waiting.length) {
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var w = waiting.shift();
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w(line);
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}
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else lines.push(line);
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})
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;
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var vars = {};
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return Chainsaw(function (saw) {
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this.getline = function (f) {
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var g = function (line) {
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saw.nest(f, line, vars);
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};
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if (lines.length) g(lines.shift());
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else waiting.push(g);
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};
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this.do = function (cb) {
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saw.nest(cb, vars);
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};
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});
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}
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And now for the new Prompt() module in action:
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var util = require('util');
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var stdin = process.openStdin();
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Prompt(stdin)
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.do(function () {
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util.print('x = ');
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})
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.getline(function (line, vars) {
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vars.x = parseInt(line, 10);
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})
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.do(function () {
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util.print('y = ');
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})
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.getline(function (line, vars) {
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vars.y = parseInt(line, 10);
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})
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.do(function (vars) {
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if (vars.x + vars.y < 10) {
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util.print('z = ');
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this.getline(function (line) {
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vars.z = parseInt(line, 10);
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})
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}
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else {
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vars.z = 0;
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}
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})
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.do(function (vars) {
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console.log('x + y + z = ' + (vars.x + vars.y + vars.z));
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process.exit();
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})
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;
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Installation
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============
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With [npm](http://github.com/isaacs/npm), just do:
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npm install chainsaw
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or clone this project on github:
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git clone http://github.com/substack/node-chainsaw.git
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To run the tests with [expresso](http://github.com/visionmedia/expresso),
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just do:
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expresso
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Light Mode vs Full Mode
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=======================
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`node-chainsaw` supports two different modes. In full mode, every
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action is recorded, which allows you to replay actions using the
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`jump()`, `trap()` and `down()` methods.
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However, if your chainsaws are long-lived, recording every action can
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consume a tremendous amount of memory, so we also offer a "light" mode
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where actions are not recorded and the aforementioned methods are
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disabled.
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To enable light mode simply use `Chainsaw.light()` to construct your
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saw, instead of `Chainsaw()`.
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