Observable Expressions

Observable Expressions watch for data changes that match a particular pattern.

This is accomplished by leveraging advanced Reactive (Rx) techniques.

Observable Expressions may contain any of Boolean Functions, Scalar Functions or Observable Functions.

Observable Functions

There are 4 main Observable Functions available in an Observable Expression:

ROW_CHANGE

This observes changes in each row in isolation - essentially there is one observer per row.

This allows users to create Alerts saying "tell me if any Row performs a particular change 3 times".

GRID_CHANGE

This observes changes in the entire grid.

This allows users to create Alerts saying 'tell me if nothing in the Grid changes for 5 minutes".

ROW_ADDED

This observes when new Rows have been added to the Grid.

It can take no arguments (any Row is added) or a Count and / or a Timeframe.

ROW_REMOVED

This observes when new Rows have been added to the Grid.

It can take no arguments (any Row is removed) or a Count and / or a Timeframe.

Observable Function Parameters

Each Observable Function has 2 mandatory parameters:

TIMEFRAME

The timeframe is the period of time in which the Observable operates.

This may be defined as a number of:

• seconds (e.g. 30s)
• minutes (e.g. 15m)
• hours (e.g. 8h)

CHANGE_TYPE

This defines the type of change that is being observed by AdapTable.

There are 4 different Change Types available:

• MIN - its the smallest change of note in the specified column

• MAX - its the largest change of note in the specified column

• NONE - no changes have occurred in the specified column

• COUNT - a given amount of changes have occurred in the specified column

  Note

  COUNT requires an additional numeric param, specifying how many changes are required to fulfill the Expression

Examples

Tell Me When...

 // The ItemCount value in a Row changes 3 times within a 5 minute timeframe
 ROW_CHANGE( COUNT( [ItemCount], 3) , TIMEFRAME('5m') )

 // An Order Cost cell contains its highest value within the last hour
 ROW_CHANGE( MAX( [OrderCost] ), TIMEFRAME('1h') )

 // The Price column has not ticked - in any row in the Grid - for the last 30 seconds
 GRID_CHANGE( NONE( [Price] ), TIMEFRAME('30s') )

 // A Row has been added to the Grid
 ROW_ADDED()

 // 3 Rows have been removed from the Grid in the last 5 minutes
 ROW_REMOVED(3, TIMEFRAME('5m') )

WHERE Clause

Optionally, a WHERE clause may be appended to the Observable Expression.

This is a Standard Expression which narrows down the scope of the 'main' part of the Expression.

 // The ItemCount value in a Row changes 3 times within a 5 minute timeframe for Active Trades
 ROW_CHANGE( COUNT([ItemCount], 3), TIMEFRAME('5m')) WHERE [Status] = 'Active'

 // No change has occurred in last 15 minutes in the Price column for rows where currency is dollar
 GRID_CHANGE( NONE([Price]), TIMEFRAME('15m')) WHERE [Currency] = 'USD'

Configuring TimeFrame Size

// Hold Data Changes for 12 hours
  expressionOptions:{
    maxTimeframeSize: 43200000,
};