Mendix Expression Language

Mendix Expression Language (MEL)

To work with Mendix objects in rules, this module has developed Mendix Expression Language. By using this expression language you can:

• Get value of an attribute of passed InputData so that you can define a Condition based on the value
• Set value to an attribute of passed InputData or OutputData
• Call a Microflow to more things within Mendix
• And more support is coming...

How to get value of an attribute?

It's simple, $(mx.getVal.input.attributeName). This should be used in Condition only.

For example if you have an entity named Person with one of the attribute as Gender (of type enum) and you have passed an object of this entity as InputData to the "RulesExecutor" JavaAction then you can write condition like $(mx.getVal.input.Gender) == "Male". This condition will be satisfied if passed object has set Gender as Male.

How to set value to an attribute?

It's simple again, $(mx.setVal.input.attributeName = value). This should be used in Action only.

Let's take the same example of Person entity and this time you want to set Gender to Male then your action should have $(mx.setVal.input.Gender = Male).

If in case you want set value to OutputData then $(mx.setVal.output.attributeName = value) should be written

How to call a Microflow?

Use $(mx.callMF.moduleName.microflowName). This should be used in Action only.

For example if you have a Microflow named as "MyFirstMicroflow" with module "MyFirstModule" then your expression should be $(mx.callMF.MyFirstModule.MyFirstMicroflow).

The InputData object will always be passed to calling Microflow. Microflow should not return anything.

Can we combine multiple conditions?

Yes, you can. Just separate each condition by a semicolon (;)

Like, $(mx.setVal.input.Gender = Male); $(mx.callMF.MyFirstModule.MyFirstMicroflow);. This action expression will set the value as well as call the specified Microflow.