Predicate functions

In many cases we have some attributes that require Boolean values. For example: hidden or disabled
Of course we can always set this value directly to True or False, in to make these functionalities useful, we will need to test the values of variables, parameters or records.
Being able to test those values and to specify the conditions that will lead to True or False allows us to implement useful interfaces.

For example, we can hide or display a group based on the value of a variable. This variable can be set as the target of a selection widget for instance. This way, we can adjust the interface responding to user interaction.
The structures to test values are called Predicates and we have many options depending of the variable type.

The string predicate takes as a parameter one string variable, parameter or record column. The general structure is :

StringPredicate ( variable ) {
    when "value" then True/False
    when IsEmpty then True/False
    otherwise then True/False
}

We can have several conditions that will be evaluated in order, and we can always end with the keyword otherwise. The return value of a predicate should always be True or False.

For example:

Group {
    hidden: StringPredicate ( selectedIdentityUid ){
        when IsEmpty then True
               otherwise False
    }
}

This group will be hidden when the variable selectedIdentityUid is empty.

The int predicate takes as a parameter one integer variable, parameter or record column. The general structure is :

IntPredicate ( variable ) {
    when InvalidInteger then True/False
    when = 0 then True/False
    when < 10 then True/False
    otherwise True/False
}

We can have several conditions that will be evaluated in order, and we can always end with the keyword otherwise. The return value of a predicate should always be True or False.

For example:

Group {
    hidden: IntPredicate ( selectedIdentityRecorduid ){
     when InvalidInteger then True
     when =0 then True
     otherwise False
 }
}

This group will be hidden when the variable selectedIdentityRecorduid is an invalid integer or equals 0.

The boolean predicate takes as a parameter one boolean variable, parameter or record column. The general structure is :

BooleanPredicate( variable )

There are no conditions and the result will be the value of the variable.

For example:

Group {
    hidden: BooleanPredicate ( showMore )
}

This group will be hidden when the variable showMore is True.

The date predicate takes as a parameter one Date variable, parameter or record column. The general structure is :

DatePredicate ( variable ) {
    when DateAfter DateLDAP(date) then True/False
    otherwise True/False
}

We can have several conditions that will be evaluated in order, and we can always end with the keyword otherwise. The return value of a predicate should always be True or False.

The supported keywords for when are: DateAfter, DateBefore, DateBetween, TimeAfter, TimeBefore, TimeBetween.

For example:

Group {
 hidden: DatePredicate (date){
 when DateAfter DateLDAP ( "20161231" ) then True
 otherwise False
 }
}

This group will be hidden when the variable date is after the given date 20161231.

The multivalied predicated can test if a value is contained in a multivalued variable.

For example:

Group {
    hidden: MultivaluedPredicate ( multivaluedVariable contains "value")
}

This group will be hidden when "value" is part of the variable multivaluedVariable.

The feature predicate test if the current user has the given feature. Syntax is bit different:

FeaturePredicate feature_id

There are no parenthesis and no conditions. It will be True if the user has the given feature.

For example:

Group {
 hidden: Not FeaturePredicate seeMore
}

This group will be hidden if the user has the feature seeMore.

Before taking a look ad the predicate functions, it is important to know that all Predicate functions will return a boolean value (True/False).
All boolean values can be transformed to the opposite value using the keyword Not.

For example:

Group {
 hidden: Not FeaturePredicate seeMore
}

This group will be hidden if the user does not has the feature seeMore.

It is also possible to combine different Predicate functions together using the AndPredicate and OrPredicate, the structures:

AndPredicate {
    Predicate1
    Predicate 2
}

OrPredicate {
    Predicate1
    Predicate 2
}

For example:

Group {
    hidden: OrPredicate {
 BooleanPredicate( variable1 )
 BooleanPredicate( variable2 )
    }
}

This group will be hidden when either variable1 is True or variable2 is True.