mirror of
https://github.com/meteor/meteor.git
synced 2026-05-02 03:01:46 -04:00
42 lines
1.5 KiB
Markdown
42 lines
1.5 KiB
Markdown
# ReactiveVar
|
|
|
|
To use `ReactiveVar`, add the `reactive-var` package to your project by running
|
|
in your terminal:
|
|
|
|
```bash
|
|
meteor add reactive-var
|
|
```
|
|
|
|
<ApiBox name="ReactiveVar" />
|
|
|
|
|
|
A ReactiveVar holds a single value that can be get and set, such that calling
|
|
`set` will invalidate any Computations that called `get`, according to the
|
|
usual contract for reactive data sources.
|
|
|
|
A ReactiveVar is similar to a Session variable, with a few differences:
|
|
|
|
- ReactiveVars don't have global names, like the "foo" in `Session.get('foo')`.
|
|
Instead, they may be created and used locally, for example attached to a
|
|
template instance, as in: `this.foo.get()`.
|
|
|
|
- ReactiveVars are not automatically migrated across hot code pushes,
|
|
whereas Session state is.
|
|
|
|
- ReactiveVars can hold any value, while Session variables are limited to
|
|
JSON or EJSON.
|
|
|
|
An important property of ReactiveVars — which is sometimes a
|
|
reason for using one — is that setting the value to the same
|
|
value as before has no effect; it does not trigger any invalidations.
|
|
So if one autorun sets a ReactiveVar, and another autorun gets the
|
|
ReactiveVar, a re-run of the first autorun won't necessarily trigger
|
|
the second. By default, only primitive values are compared this way,
|
|
while calling `set` on an argument that is an _object_ (not a
|
|
primitive) always counts as a change. You can configure this behavior
|
|
using the `equalsFunc` argument.
|
|
|
|
<ApiBox name="ReactiveVar#get" instanceName="reactiveVar" />
|
|
|
|
<ApiBox name="ReactiveVar#set" instanceName="reactiveVar" />
|