Usage and Manipulation of Variables

Variables are tightly integrated into the whole Better EHR Studio structure and you can use them in different areas.

The table below shows where you can use each type of variable.

usage \ variable type	static variable	externally/internally defined	AQL variable
dependencies when clause	✅	✅	⬜️
dependencies then clause	⬜️	✅	⬜️
expression	✅	✅	✅
rich text	✅	✅	⬜️
html element	✅	✅	⬜️
aql building	⬜️	✅	⬜️
column/stacked list valueset	⬜️	⬜️	✅
dropdown inputs	⬜️	⬜️	✅
javascript API	✅	✅	✅

Some practical examples:

When / Then Clauses

When a clause is a condition clause, something else will happen when something is in a given state.

A quintessential example would be:

When isFormPrefilled equals true, then date stored is shown.

With when / then clauses, you add interactivity to the form. You can see how the variables change and then change something else in the form according to a specific variable value.

Expressions

Expressions help calculate and transform data, e.g., format date, BMI formula, and concatenating text.

Examples of Using Variables

The following chapters will present practical examples of using variables.

Using Variables in Dependency When / Then Clauses

Static Variable in a When Clause

The above example shows how to display a warning message with rich text and show it only when a form is in read-only mode.

The 'when' clause in the example is:

When isReadOnly equals true, then warning show, otherwise warning hide.

The result of the interaction is a warning that is displayed when you put a form into read-only mode.

Internally Defined Variable in a Then Clause

When you want to change a value of a variable based on user input, you can use the 'then' clause. For example, you would use it to calculate a patient score based on the patient data.

In the example below, we calculated the score based on the patients BMI, unplanned weight loss and presence of an acute disease:

NOTE: Static and AQL variables cannot be changed. The values of static and AQL variables are omitted, because the clause would change otherwise. Even though the definition of an externally defined variable is that it comes from outside the Form renderer, you can still change its value inside the form.

Internally Defined Variable in a When Clause

Based on the calculated score, you can now show the appropriate risk-rich text.

For example:

• if the score is 0, then you show Low risk rich text,
• if the score is 1, then you show Medium risk rich text, and
• if the score is 2, then you show High risk rich text.

Now, based on the patient data, the form alerts the doctor of the health risk.

Expressions

Expressions help you format and manipulate data. You can find expressions in different locations of the Form Builder.

NOTE: Writing expressions is easier with Expression Assistant. Visit the Expression Assistant documentation to learn more.

Static Variable Expression

In the above example, you use the currentDateTime variable in a 'then' clause, and then use the expression to format the date.

Internal Variable Expressions

In the same way, you can add expressions to internally defined variables.

In the above example, we calculated the internally defined variable HEART_1 by adding the History, EKG, and Age values.

AQL Variable Expressions

AQL variables get its value from an AQL query result.

The picture shows weight_aql variable example that reads the body weight from a composition.

You can also manipulate the value of an AQL variable with an expression.

The example shows how you can use 'when' and 'then' clauses to calculate BMI from a patient's weight when weight is obtained through an AQL.

Rich Text and HTML Elements

Both Rich text and HTML elements use a Mustache templating engine, and you can use the defined variables inside this generic.

The example shows the currentDate static variable and an internally defined variable score inserted into Rich text.

Please, visit the Rich text documentation and HTML element documentation to learn more.

Column / Stacked List Valueset

Column / stacked list lets you display an AQL result in a list. For more information, please visit the Column list documentation.

In the example above, there is a column list showing the results from the weight_patient_aql variable. Weight_patient_aql variable executes an AQL query that reads weight from compositions.

Columns displaying results can use expressions. You can add expressions to the label input.

For example, you can concatenate the bodyweight column to show both the magnitude and unit.

You can also format the date of the weight measurement.

Dropdown Inputs

Dropdown inputs have a label and a value. Both can use an expression.

The example shows a dropdown input that displays data from an AQL variable. The label has a FORMAT_DATE expression, and the value displays the weight magnitude.

JavaScript API

To use JavaScrip API, you need advanced JavaScript knowledge.

The following example shows how to execute AQL and set a field value.

When the Manual input checkbox is ticked, the form is emptied and inputs appear. Otherwise, the form is filled with variable values and inputs are disabled.

An example of a code:

api.addListener('generic-boolean-xxxxx', 'CHANGE', function(model) {

  let date = api.getVariable('currentDate').value;
  let patient = api.getVariable('ehrId').value;
  let weight_aql = api.getVariable('weight_aql').value.code;

  var value = api.getFieldValue('generic-boolean-xxxxx');
  if (value === true) {
    api.clearFormElement('patient_id');
    api.enableFormElement('patient_id');
    api.clearFormElement('patient_weight');
    api.enableFormElement('patient_weight');
    api.clearFormElement('date');
    api.enableFormElement('date');
  } else {
    api.setFieldValue('patient_id', patient);
    api.disableFormElement('patient_id');
    api.setFieldValue('date', date);
    api.disableFormElement('date');
    api.executeAql(weight_aql).then( data => api.setFieldValue('patient_weight', data.resultSet[0].weight, 'magnitude'));
    api.disableFormElement('patient_weight');
  }
})