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Implementing and Using Formatter Functions

Objective

After completing this lesson, you will be able to Implement and use formatter functions to convert model data into an external format.

Creating Formatter Functions

SAPUI5 provides two different options to convert model data to an external format for visual representation: data types and formatter functions.

While data types provide the possibility to format, parse and validate data, formatter functions allow one-way conversion only.

A formatter function has a single parameter, which is the value which needs to be formatted to an external representation.

A formatter function can be used not only to format a value, but also to do type conversion or calculate results from a given value.

Note

When using formatter functions, the binding is automatically switched to "one-way". So you can’t use a formatter function for "two-way" scenarios.

Formatter functions can be defined in a separate module or locally in a view controller.

Note

It is recommended to use a separate module file that groups the formatters and makes them globally available in the application.

The coding example in the figure Defining a Formatter Function shows the definition of a formatter function called classText. It is created in a separate module that is implemented in the formatter.js file. The classText formatter translates keys used in the model data into texts that are understandable to the user. For example, for the key value "Y", the text "Economy Class" is returned.

Using Formatter Functions

The figure, Using a Formatter Function, shows how a formatter function defined in a separate module can be used in an XML view.

To do this, it must first be ensured that the module containing the formatter function is loaded. This is achieved by requiring the formatter module by its module name in the <mvc:View> tag, as shown in the figure.

The loaded module is assigned to the alias formatter. The name of this alias is arbitrary, the crucial thing is that the alias can be used as a variable in the binding.

To specify the formatter function in the binding, the complex binding syntax is used. The model property to be formatted is specified via the path property, and the formatter function is assigned to the formatter property via the following syntax:

Code Snippet

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<alias of the formatter module>.<name of the formatter function>.

So in the example, the content of the Class model property is passed to the classText formatter function . The string returned by this formatter function is then displayed on the UI via the Text control.

Note

In addition to custom formatter functions, you can also use predefined formatter functions for standard use cases, such as sap/base/strings/formatMessage.

Implement a Formatter Function

Business Scenario

In the booking table, the booked class of a flight is currently displayed using the values C, Y, and F respectively. In this exercise, you will implement a formatter function to convert these technical values from the Class model property into a meaningful text for the user. For C, the text Business Class, for Y, the text Economy Class, and for F, the text First Class should be set. Then you will integrate the implemented formatter function into the data binding of the corresponding table column in order to format the flight class accordingly.

Template:	Git Repository: https://github.com/SAP-samples/sapui5-development-learning-journey.git, Branch: `sol/14_data_types`
Model solution:	Git Repository: https://github.com/SAP-samples/sapui5-development-learning-journey.git, Branch: `sol/15_formatters`

Task 1: Create the Formatter Function

Steps

Create a new file named formatter.js in the subfolder model of the webapp folder.
1. Open the context menu for the webapp/model folder in the project structure.
2. Select New File.
3. In the New File dialog that appears, type formatter.js and choose OK.
Result
The formatter.js file is created and displays in the editor.
Add the following code to the formatter.js file to create a formatter function named classText that transforms passed values from the model into meaningful texts.
Code Snippet
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```
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sap.ui.define([], function () {
  "use strict";

  return {

    classText: function (sClass) {
      switch (sClass) {
        case "C":
          return "Business Class";
        case "Y":
          return "Economy Class";
        case "F":
          return "First Class";
        default:
          return sClass;
      }
    }

  };

});
```

Result

The formatter function should be implemented as follows:

Task 2: Use the Formatter Function for the Display of the Flight Class

Steps

Open the Overview.view.xml file from the webapp/view folder in the editor.
Add the following attribute to the <mvc:View> tag:
Code Snippet
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```
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core:require="{formatter: 'sap/training/exc/model/formatter'}"
```
Note
The additional attribute ensures that the module with the classText formatter function is loaded and assigns it to the formatter alias.
Result
The <mvc:View> tag should now be similar to the following:

Adapt the data binding for the flight class column (model property Class) in the booking table as follows to transfer the content of the Class model property to the external representation via the formatter function:

`Old`	`New`
Code Snippet Copy code Switch to dark mode `1 <Text text="{Class}"/>`	Code Snippet Copy code Switch to dark mode `1234 <Text text="{ path: 'Class', formatter: 'formatter.classText' }"/>`

Result

The data binding for the flight class column in the booking table should now look like this:

Test run your application by starting it from the SAP Business Application Studio.
Make sure that the technical values from the data model (C, Y, or F) are no longer displayed in the flight class column of the booking table, but the meaningful texts from the formatter function.
1. Right-click on any subfolder in your sapui5-development-learning-journey project and select Preview Application from the context menu that appears.
2. Select the npm script named start-noflp in the dialog that appears.
3. In the opened application, check if the component works as expected.

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