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Cluster
It creates a master Observable of the combined value of its members by merging all the provided Observable constructs. Whenever any of these wrapped constructs emits a value, Cluster emits a new combined-value.
It also provides direct access to the wrapped constructs through
items property.
The ideal use case would be when you need access to the combined value of some ActiveJS constructs as an Observable.
Basically,
- It creates a master Observable of the combined -value of provided members.
- Provides access to its members through the Cluster.
- Provides static access to the combined-value.
Initializing a Cluster:
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// a ListUnit that saves user's liked things
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const userLikesUnit = new ListUnit();
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// a DictUnit that saves user's preferences as key:value pairs
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const userPreferencesUnit = new DictUnit({initialValue: {humor: 'dark'}});
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// create a Cluster to group the above Units together
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const userDataCluster = new Cluster({
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userLikesUnit, // using shorthand notation
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userPreferencesUnit
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});
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Accessing the value:
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// subscribe for the combined-value
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userDataCluster.subscribe(value => console.log(value))
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// or access it directly
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console.log(userDataCluster.value())
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// both of these will log the following
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{
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userLikesUnit: [],
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userPreferencesUnit: {humor: 'dark'}
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}
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Accessing the members through Cluster:
Cluster members can be accessed through the
items property.1
console.log(userDataCluster.items.userPreferencesUnit.value());
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// logs {humor: 'dark'}
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console.log(userDataCluster.items.userLikesUnit.value());
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// logs []
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Value propagation:
Whenever a member of the Cluster emits a value, the Cluster will emit a new combined value.
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// set a preference to the userPreferencesUnit
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userPreferencesUnit.set('favouriteMovie', 'Matrix');
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// the Cluster will emit the following value
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{
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userLikesUnit: [],
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userPreferencesUnit: {humor: 'dark', favouriteMovie: 'Matrix'}
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}
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// add some liked things to the userLikesUnit
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userLikesUnit.push({id: 42, label: 'puppy'}, {id: 66, label: 'kitten'});
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// the Cluster will emit the following value
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{
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userLikesUnit: [{id: 42, label: 'puppy'}, {id: 66, label: 'kitten'}],
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userPreferencesUnit: {humor: 'dark', favouriteMovie: 'Matrix'}
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}
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Similarly, we can group any number of Units, Systems, Actions or even Clusters together.
Notes
- Try to refrain from using the static value accessor
value()method when the Cluster contains immutable Units because when calling thevalue()method of a Cluster, it internally calls its members'value()method, and if members are Immutable Units, those Units would create a clone on every call. It's not a bad thing if used intentionally, but it can add extra overhead if used too often.
Configuration Options
The configuration options can be passed at the time of instantiation. All the configuration options are optional. Some options can also be set globally. See Configuration for more details.
Last modified 1yr ago