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Merge remote-tracking branch 'origin/rewrite' into rewrite

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Leo Horie 2017-01-11 13:36:28 -05:00
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docs/lifecycle-methods.md
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@ -65,7 +65,7 @@ var ComponentWithState = {
this.data = vnode.attrs.data this.data = vnode.attrs.data
}, },
view: function() { view: function() {
return m("div", this.data) return m("div", this.data) // displays data from initialization time
} }
} }
@ -194,64 +194,6 @@ This hook is useful to reduce lag in updates in cases where there is a overly la
Although Mithril is flexible, some code patterns are discouraged: Although Mithril is flexible, some code patterns are discouraged:
#### Do not redraw synchronously from lifecycle hooks
The [`m.render`](render.md) method modifies DOM state, and therefore it's [non-reentrant](https://en.wikipedia.org/wiki/Reentrancy_(computing)). All lifecyle methods are called by `m.render()`, and therefore you cannot call `m.render`, `m.mount`, `m.route` or `m.redraw` from a lifecycle method. Redrawing synchronously from a lifecycle method will result in **undefined behavior**.
Typically, redrawing from an `oninit` or `onbeforeupdate` hook is meaningless since the element in question renders shortly after them anyways. If redrawing is required from any other hooks, you should consider moving code up the execution path; for example, refactor it so that the application code runs on an event handler, before its natural redraw occurs.
```javascript
// AVOID
var greeting = ""
var BrokenComponent = {
onupdate: function() {
this.greeting = greeting()
m.redraw()
},
view: function() {
return m("div[title=Hello]", {onclick: m.withAttr("title", function(v) {greeting = v})}, this.greeting)
}
}
// PREFER
var greeting = ""
var WorkingComponent = {
view: function() {
return m("div[title=Hello]", {onclick: m.withAttr("title", function(v) {greeting = v})}, greeting)
}
}
```
On rare occasions, there may not be a way to refactor a redraw out of a lifecycle method due to dependencies on layout values (e.g. scrollbar position, an element's updated offsetHeight, etc). In those cases, you should redraw asynchronously, by wrapping the redraw call in a `requestAnimationFrame`, `setTimeout` or similar function.
```javascript
// AVOID
var BrokenComponent = {
onupdate: function(vnode) {
var oldWidth = this.width
this.width = vnode.dom.offsetWidth
if (oldWidth !== this.width) m.redraw()
},
view: function() {
return m("div", {onclick: function() {console.log("calculating width")}}, "Width is: " + this.width)
}
}
// PREFER
var WorkingComponent = {
onupdate: function(vnode) {
var oldWidth = this.width
this.width = vnode.dom.offsetWidth
if (oldWidth !== this.width) requestAnimationFrame(m.redraw)
},
view: function() {
return m("div", {onclick: function() {console.log("calculating width")}}, "Width is: " + this.width)
}
}
```
#### Avoid premature optimizations #### Avoid premature optimizations
You should only use `onbeforeupdate` to skip diffing as a last resort. Avoid using it unless you have a noticeable performance issue. You should only use `onbeforeupdate` to skip diffing as a last resort. Avoid using it unless you have a noticeable performance issue.