Context variables allow the creation of components built in a functional way. The creator of a component can define many arbitrary context variables, which can then be used by the user in functions defined as parameters of that component.

An example of such a component could be a validator, which allows you to validate data in a dynamic table. A context variable $currentRow is then provided, storing the index of the current row in the table. The only parameter would be a function that would return a logical value saying whether the row is valid or not

The action configured this way will mean that the not(empty(item($currentRow, $Nazwa Dostawcy))) function will be called for each row with a changing $currentRow parameter:

• not(empty(item(0, $Nazwa Dostawcy)))
• not(empty(item(1, $Nazwa Dostawcy)))
• not(empty(item(2, $Nazwa Dostawcy)))

This allows us to create more versatile components. Also, we don't need to create multiple function overloads, for example, for array parameters - it's enough to use a component that allows iteration over rows of such arrays.

Defining context variables

Defining context variables (ContextVariable) is done at the stage of creating the component definition. Below is an example of adding one context variable for a validator:

@Define
public void definition( ValidatorDefinitionBuilder builder )
{
    builder
        .id( "contextVariableExample" )
        .name( "Context Variable Example" )
        .category( Categories.TEST )
        .contextVariable()
            .id( "currentRow" )
            .name( "currentRow" )
            .description( "Current table row index" )
            .type( Types.INTEGER )
            .create()
        .parameter()
            .id( "fn" )
            .name( "Function" )
            .type( Types.FUNCTION )
            .create();
}

Determine the value of context variables

The value of context variables is set using an object ContextVariables that can be injected as a parameter of a component method. Just add a type ContextVariables

parameter to the component method (e.g. validate for validator) 

and use the set(id, value) method:

public void validate( @Param FunctionCall fn, ContextVariables contextVariables, ValidationErrors errors )
{
    int length = ...; // liczba wierszy
    for ( int i = 0; i < length; i++ )
    {
        contextVariables.set( "currentRow", i );
        if ( !fn.<Boolean> call() )
        {
            errors.add( "Validation errror" );
        }
    }
}

Context variables in form actions

Due to the different environment of running form actions, the way of setting these variables is a little different. We set the value of context variables using the setContextVariable PW.form.action.Action class:

 PW.FormActions.create('context-var-example', {
	defaultActions: {
		variableSet: function(vs, added, updated, removed) {
			this.invoke(vs);
		}
	},
	invoke: function(vs) {
		var fn = this.get('fn');
		var target = this.get('target');
 
		PW.each(vs.getRecords(), function(record, index) {
			this.setContextVariable("currentRow", index);


			var newValue = fn.call();
			target.setItemValue(newValue, index);
		}, this);
	}
});