The filter function filters the objects from an array based on some condition.

Syntax

filteredArray = filter(array, booleanExpression)

Inputs

array : a reference to an array.

booleanExpression : conditional expression to filter the objects in the array.

Output

filteredArray : filtered array based on the condition.

Example flow

Schema w2Schema {
  w2 [
    string employerName
    number wages
  ]
}

value income -> w2Schema {
  w2 [
     {
       "Intuit, Inc.
       105000
     }
     {
       "Uber
       10000
     }
  ]
}

Schema thresholdSchema {
  number wages
}

value threshold -> thresholdSchema { 100000 }

Mapping finalMapping input income, threshold output w2Schema as output {
  output.w2 = filter(income.w2, employerName == "Intuit, Inc." && wages > ::threshold.wages)
}

Flow filterFlow {      
  Start finalMapping {
  }
}

Output for Example Flow

{ 
  w2 :  [{ employerName : "Intuit, Inc.", wages : 105000 }
}

Explanation

The condition is employerName == "Intuit, Inc." && wages > ::threshold.wages.

The first part of the condition says employerName == "Intuit, Inc.". The context of the variable employerName here is the array, which is income.w2. (You don't have to specify the whole path i.e income.w2.employerName to filter the w2s).

The second part of the condition says wages > ::threshold.wages". The variable wages here is within the context of w2 but if you want to refer something which is outside the scope of w2, you need to refer it with a global scope operator ::