# Composite components ## Introduction A composite component allows you to encapsulate a piece of an application screen into a consistent, reusable element.\ The component defines both the appearance of the screen area and its behavior. Teams using composite components to build user interfaces save time and make it easier to maintain frontend consistency. ### **Role and uses** The main role of composite components is **multiple reuse** of repeatable form areas on different pages. Once created, a composite component can be embedded: * on different form pages – so that many pages can use a shared, consistent section * multiple times on the same page – e.g. if one form needs two independent address sections (for residential and correspondence addresses). This approach significantly speeds up application development and makes maintenance easier – a change in the definition of a composite component automatically affects all places where it has been used. This increases application consistency (the same components look and behave identically in different forms) and reduces the risk of errors resulting from duplicated configuration. For example, if a form needs a repeating section with the same fields (such as the aforementioned address section), it is worth separating it into a composite component and using it multiple times instead of creating those fields from scratch every time. Composite components are often used in business applications as standard form sections (e.g. address details, contact details, customer information sections, etc.), which ensures a uniform user experience and makes it easier to develop future forms.

Figure 1. "Composite components" in the "Library" module

## Creating a component To create a new composite component or edit an existing one, you need to: 1. In **Eximee Designer** go to the module **Library** and select the tab **Composite components,** 1. this view displays a list of all available composite components in the repository along with management options, 2. From the list, you can: 1. create a new component (button **Add composite component**), 2. copy or edit an existing artifact using the drop-down menu (three dots) 3. view the component version history using the drop-down menu (three dots) 3. Select the option to add a new composite component 1. the artifact creation window appears, where you enter the component name and location (folder) in the project tree, similarly to creating a new form.

Figure 2. "Window with the list of composite components in the library"

After creating the composite component artifact, the **composite component editor**opens, very similar to the form editor. In the center of the view, we design the layout and add the required fields and controls – you can drag base components onto the work area (e.g. text fields, lists, buttons, etc.) or even nest other available composite components. This is how we define the internal structure of the new composite component. On the right side there is a properties panel where we configure the attributes of the selected fields (as in a form). After configuring the content of the composite component, we save it by assigning the appropriate version (more about versioning below). Saving creates a new version of the artifact, which can be used in forms.

Figure 3. "Composite component editor window – designing content"

## Parameters **input** Composite components can accept **input parameters**, which allows values to be passed into them from outside – from a form or even from another composite component. To define an input parameter, in the composite component definition editor you need to select the option in the left panel **Input parameters**, and then click **Add input parameter.** Each input parameter refers to some field or session variable from the **embedding** context of the component (i.e. it will expect a specific field/variable to be assigned when the component is used). When defining a parameter: * we specify the source of the value (form field or variable), * optionally assign an *alias* (a friendly name shown during mapping) * optionally provide a default value – used if no value is assigned during embedding. It is possible to map values from fields in the parent form, fields from other composite components on the same form, as well as session variables available in the form context. Thanks to the input parameter mechanism, a composite component can be more universal – for example, instead of referring to a specific global variable inside, it can accept the value as a parameter, which allows it to be used in different places with different data.

Figure 4. "Input parameter configuration panel in the composite component editor"

## Embedding a component A created composite component can be embedded in any form or even inside another composite component (nesting) – the platform allows any nesting depth. To use a composite component in a form, go to editing that form, and then from the component palette on the left select the tab **Composite**. A list of all available composite components in the repository will be displayed (with the ability to search by name). From this list, select the appropriate component and add it to the form by drag and drop to the desired place in the form structure. After dropping it, the composite component will be embedded in the form as one logical whole – in the form structure tree it will be visible as a single node containing the fields defined earlier. {% hint style="info" %} If the embedded composite component has defined input parameters, after adding it to the form **you need to configure the mapping of these parameters**, assigning the appropriate fields or values in the context of the form or parent component. In the form editor, this is done in the section **Input parameters** in the properties of the embedded component – just select the composite component on the form and click the pencil icon next to the field *Input parameters*, to open the mapping window. {% endhint %}

Figure 5. "Window for mapping input parameters when embedding a composite component in a form"

A composite component placed on the screen becomes an integral part of it. All fields it contains inherit the behavior of standard fields – e.g. required fields must be filled in, validators attached to fields inside the composite component work in the same way as for fields added directly to the form, etc. If needed, at the form level you can also define additional **form validators** covering fields inside composite components as well (e.g. a script checking consistency of data between sections). Similarly, navigation mechanisms or conditional visibility also work for nested components – a composite component can, for example, be hidden or shown depending on a condition, just like a single field. ## Versioning and propagation of changes Versioning is described in detail [here](/documentation/documentation-en/budowanie-aplikacji/aplikacja-biznesowa/wersjonowanie.md). ## Interactions with other artifacts A composite component does not function in a vacuum – it interacts with various elements of the platform ### Forms The basic "relationship" is embedding in a form, which was discussed above. From the form's point of view, a composite component is simply a form element – during application runtime, the end user does not see any difference between fields originating from a composite component and other fields. In the **Translations tab** of the form, all texts contained in embedded composite components are available for editing – this means that translations of labels and hints from the composite component can be overridden or adjusted at the level of a specific form, if necessary. The composite component is also treated as a part of the application. ### Validators Fields within a composite component can use all validation mechanisms available for standard fields. If we assign a **script validator**to one of the fields inside a composite component, it will be executed in the same way as for a standard field on the form. Also **visibility conditions** or **required conditions** can be defined for fields inside a composite component – they will be respected after the component is embedded in the form. Moreover, validators defined at the entire form level (e.g. verifying dependencies between different fields) can refer to fields located in composite components. Such a field can be identified by its **business identifier (mid)** – composite components and their fields have business identifiers just like ordinary form fields, which makes it easier to refer to them in scripts and configurations. ### Formatted content Composite components can also use **content artifacts** (TextContent), similarly to ordinary forms. If a section requires embedding a larger block of static text (e.g. terms, clauses, descriptions), you can add a control of type **Formatted content** in the composite component and bind a Content artifact containing the appropriate content (centrally managed) to it. This way, the composite component can contain not only data fields, but also informational elements or user instructions, making it a complete, reusable fragment of the user interface. ### Services and variables If **session variables** are used inside a composite component (e.g. to store transient values or service results), remember to prefix the names of these variables with the symbol in conditional expressions `@.` This allows the platform to distinguish the component's session variable from the parent form's session variable. In addition, session variables cannot be used directly in components of type *Repeatable section* inside a composite component – in such cases, it is recommended to use technical fields as the value carrier. If a composite component needs to use an external service (e.g. to populate its fields based on data from a database), it can call **services** just like a form. A service can be attached as a *PageService* in the component logic and, for example, called in response to an event (e.g. a field change). However, remember that services operate in the context of the entire request, so invoking a service from within a component affects the parent form. ## **Best practices** ### **Identifying reuse opportunities** Already at the requirements analysis stage, it is worth identifying form sections that may appear repeatedly or in many different application forms. Such sections (e.g. address details, customer personal data, contact information sections, consent sections, etc.) should be designed as separate composite components instead of duplicating the same fields in many places. This makes development easier (the section is created once) and maintenance easier (modifying the section in one place updates it everywhere it is used). ### **Naming and organization** Use consistent artifact naming. A composite component should have a name that clearly indicates its content or purpose. It is common to use a convention where component names are prefixed with a prefix related to the application or business module, e.g. `crmCustomerAddress`, `insuranceVehicleData` – this makes it easier to identify in the repository which area a given component belongs to. Also maintain order in the folder structure in the Library – composite components are worth grouping into thematic or project folders. ### **Documenting a component** Each composite component can be accompanied by internal **documentation**. In the **Properties** composite component editor, there is a "Documentation" section where you can describe the component's behavior and purpose (it supports HTML formatting). It is recommended to complete the documentation for a component – especially if it will be used by many developers or in many places – so that platform users know how to apply it correctly and what its dependencies may be. Good documentation makes reuse easier and speeds up onboarding of new team members.

Figure 6. "Composite component 'Properties' tab – documentation preview"

### **Versioning and backward compatibility** When planning changes in a composite component, consider their impact on existing forms. **Avoid introducing incompatible changes** without bumping the major version (MAJOR). If a structural or behavioral change is necessary that could disrupt the operation of forms using it, it is better to create a new version branch. After modifications, test the composite component in all critical scenarios – especially when the component is used in many places. ### **Avoiding excessive complexity** Although composite components can contain any logic, try to make them fulfill a relatively uniform, clearly defined function. Avoid creating one huge composite component that handles many unrelated tasks – it is better to split it into smaller, more specialized sections. Excessive nesting of composite components (component within component within component, etc.) can also make debugging and understanding the form more difficult – use this capability judiciously, guided by the readability of the form structure. ### **Be careful with copying components** The platform allows duplicating a composite component (using the **Duplicate** option in the list of composite components) – this is useful when we want to create a similar component based on an existing one. However, **make sure how nested components are handled** when copying. If the copied composite component contained other composite components, the copy will **not create duplicates of them** – references to the original artifacts will be preserved. You need to consider whether in the new component we still want to use those original, shared subcomponents, or whether we should copy them as well (e.g. when changes to them should not affect our new component). This is important from a maintenance perspective – unintentionally editing a nested component can affect other places where it is used. ### **Using ready-made components** Check whether the composite component you need does not already exist in the library – especially in larger organizations, a catalog of shared components may be created. Using already prepared, tested components (e.g. user authentication components, downloadable documents component, GDPR consent sections, etc.) is faster and safer than building your own from scratch. Build new composite components only when the required functionality is truly missing from the existing assets. ### **UX consistency** Remember that a composite component is part of the user interface – design it in line with the UX/UI standards used in your organization. Make sure that the arrangement of fields, their labels, hints, as well as the validations and error messages within the component are consistent with the rest of the form. This way, the user will not feel that a section has been "pasted on" from somewhere else. Use the **translations** mechanism for static texts in the component, complete their keys and values – this will make literal management from the application level easier. ## Example The illustrations below show an example of a composite component named `demoAddress` and how it is used. First, a composite component containing address fields (street, city, postal code) was designed – it serves as a template for the address section:

Figure 7. Designed composite component "demoAddress" (address section)

Then the same component `demoAddress` was embedded three times in a sample form (e.g. for residential address, correspondence address, and workplace address) – thanks to reusing one artifact, we get three sections in the form without needing to create three sets of fields separately:

Figure 8. Multiple use of the composite component "demoAddress" in the form structure (embedded three times)

As a result, on the user interface the form displays three uniform address sections using the same composite component:

Figure 9. Appearance of a form with the composite component "demoAddress" embedded multiple times (three address sections)

The above example illustrates how composite components simplify the creation of repetitive parts of an application – modifying the component `demoAddress` (e.g. adding the "Country" field) will automatically add that field to all three address sections on the form. This makes managing complex forms easier, and shared fragments of the application remain consistent wherever they are used. By using the above tips and best practices, Eximee composite components make it possible to efficiently create modular, maintainable business applications in which sections defined once can be used in many processes and forms. Well-designed composite components pay off by reducing duplicated work, standardizing the interface, and accelerating future changes. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.eximee.com/documentation/documentation-en/budowanie-aplikacji/interfejs-uzytkownika/komponenty-rozszerzone/komponenty-zlozone.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.