Configuration

ActiveJS tries to give as many configuration options as possible to allow some degree of customization and personalization. While not requiring any configuration by choosing the most sensible defaults.

Configuration can be done on many levels, it can be done per instance and it can also be done globally.

Inline / per-instance configuration

// Unit configuration
const aUnit = new GenericUnit({cacheSize: 10, immutable: true, persistent: true})

// Action configuration
const anAction = new Action({initialValue: 'START'})

// AsyncSystem configuration
const anAsyncSystem = new AsyncSystem({
    freezeQueryWhilePending: true,
    
    // it overrides AsyncSystem's member Units' config
    // it applies to all three GenericUnits and one BoolUnit
    UNITS: {cacheSize: 3},
    
    // it overrides common UNITS config above, applies to dataUnit only
    DATA_UNIT: {cacheSize: 4}
})

Global configuration

ActiveJS exposes a global class called Configuration, through which you can set and reset global config that overrides default configuration. Which can still be overridden by inline config.

To set the global config you can use the set method, it accepts a configuration object of type GlobalConfig.

Configuration.set({
    // it overrides default Action config
    ACTION: {replay: true},
    
    // it overrides default Unit config, for all Unit types
    UNITS: {cacheSize: 1},
    
    // it overrides global UNITS config above, for GenericUnits
    GENERIC_UNIT: {cacheSize: 2},
    
    ASYNC_SYSTEM: {
        // it overrides global UNITS, GENERIC_UNIT, and BOOL_UNIT config
        // it applies to AsyncSystem's three GenericUnits and one BoolUnit
        UNITS: {cacheSize: 3},
        
        // it overrides global ASYNC_SYSTEM.UNITS config above, for dataUnit
        DATA_UNIT: {cacheSize: 4}
    }
});

Hierarchy of configuration

The more specific a configuration the higher precedence it has.

Given the global config type interface GlobalConfig. This is how the precedence order works, going from lowest to highest precedence.

Units	AsyncSystem	Action	Cluster
Default config	Default config	Default config	Default config
GlobalConfig > UNITS	GlobalConfig > ASYNC_SYSTEM	GlobalConfig > ACTION	GlobalConfig > CLUSTER
Type-specific Unit config e.g. GlobalConfig > DICT_UNIT	Inline config	Inline config	Inline config
GlobalConfig > ASYNC_SYSTEM > UNITS
Unit specific config e.g. GlobalConfig > ASYNC_SYSTEM > UNITS > DATA_UNIT or GlobalConfig > ASYNC_SYSTEM > UNITS > QUERY_UNIT
Inline config

Notes

• In a Single Page App, you should set global configuration only once, and override it in the inline config if needed. Otherwise, it can become very difficult to keep track of which instances are using what configuration, depending on their time of creation.

• If you do need to change global configuration multiple times, just keep in mind that calling Configuration.set second time doesn't merge the new configuration with the old one it simply rewrites it. However, the defaults are not affected by this behavior, they have to be overridden specifically every time.