143 lines
6.1 KiB
Plaintext
143 lines
6.1 KiB
Plaintext
include ../_util-fns
|
|
|
|
:marked
|
|
We can't always justify the cost and time to build handcrafted forms,
|
|
especially if we'll need a great number of them, they're similar to each other, and they change frequently
|
|
to meet rapidly changing business and regulatory requirements.
|
|
|
|
It may be more economical to create the forms dynamically, based on metadata that describe the business object model.
|
|
|
|
In this cookbook we show how to use `ngFormModel` to dynamically render a simple form with different control types and validation.
|
|
It's a primitive start.
|
|
It might evolve to support a much richer variety of questions, more graceful rendering, and superior user experience.
|
|
All such greatness has humble beginnings.
|
|
|
|
In our example we use a dynamic form to build an online application experience for heroes seeking employment.
|
|
The agency is constantly tinkering with the application process.
|
|
We can create the forms on the fly *without changing our application code*.
|
|
|
|
<a id="toc"></a>
|
|
:marked
|
|
## Table of contents
|
|
|
|
[Question Model](#object-model)
|
|
|
|
[Form Component](#form-component)
|
|
|
|
[Questionnaire Metadata](#questionnaire-metadata)
|
|
|
|
[Dynamic Template](#dynamic-template)
|
|
|
|
:marked
|
|
**See the [live example](/resources/live-examples/cb-dynamic-form/ts/plnkr.html)**.
|
|
|
|
.l-main-section
|
|
<a id="object-model"></a>
|
|
:marked
|
|
## Question Model
|
|
|
|
The first step is to define an object model that can describe all scenarios needed by the form functionality.
|
|
The hero application process involves a form with a lot of questions.
|
|
The "question" is the most fundamental object in the model.
|
|
|
|
We have created `QuestionBase` as the most fundamental question class.
|
|
|
|
+makeExample('cb-dynamic-form/ts/app/question-base.ts','','app/question-base.ts')
|
|
|
|
:marked
|
|
From this base we derived two new classes in `TextboxQuestion` and `DropdownQuestion` that represent Textbox and Dropdown questions.
|
|
The idea is that the form will be bound to specific question types and render the appropriate controls dynamically.
|
|
|
|
`TextboxQuestion` supports multiple html5 types like text, email, url etc via the `type` property.
|
|
|
|
+makeExample('cb-dynamic-form/ts/app/question-textbox.ts',null,'app/question-textbox.ts')(format='.')
|
|
|
|
:marked
|
|
`DropdownQuestion` presents a list of choices in a select box.
|
|
|
|
+makeExample('cb-dynamic-form/ts/app/question-dropdown.ts',null,'app/question-dropdown.ts')(format='.')
|
|
|
|
:marked
|
|
Next we have defined `QuestionControlService`, a simple service for transforming our questions to an ngForm control group.
|
|
In a nutshell, the control group consumes the metadata from the question model and allows us to specify default values and validation rules.
|
|
|
|
+makeExample('cb-dynamic-form/ts/app/question-control.service.ts',null,'app/question-control.service.ts')(format='.')
|
|
|
|
<a id="form-component"></a>
|
|
:marked
|
|
## Question form components
|
|
Now that we have defined the complete model we are ready to create components to represent the dynamic form.
|
|
|
|
:marked
|
|
`DynamicForm` is the entry point and the main container for the form.
|
|
+makeTabs(
|
|
`cb-dynamic-form/ts/app/dynamic-form.component.html,
|
|
cb-dynamic-form/ts/app/dynamic-form.component.ts`,
|
|
null,
|
|
`dynamic-form.component.html,
|
|
dynamic-form.component.ts`
|
|
)
|
|
:marked
|
|
It presents a list of questions, each question bound to a `<df-question>` component element.
|
|
The `<df-question>` tag matches the `DynamicFormQuestionComponent`,
|
|
the component responsible for rendering the details of each _individual_ question based on values in the data-bound question object.
|
|
|
|
+makeTabs(
|
|
`cb-dynamic-form/ts/app/dynamic-form-question.component.html,
|
|
cb-dynamic-form/ts/app/dynamic-form-question.component.ts`,
|
|
null,
|
|
`dynamic-form-question.component.html,
|
|
dynamic-form-question.component.ts`
|
|
)
|
|
:marked
|
|
Notice this component can present any type of question in our model.
|
|
We only have two types of questions at this point but we can imagine many more.
|
|
The `ngSwitch` determines which type of question to display.
|
|
|
|
In both components we're relying on Angular's **ngFormModel** to connect the template HTML to the
|
|
underlying control objects, populated from the question model with display and validation rules.
|
|
|
|
<a id="questionnaire-metadata"></a>
|
|
:marked
|
|
## Questionnaire data
|
|
:marked
|
|
`DynamicForm` expects the list of questions in the form of an array bound to `@Input() questions`.
|
|
|
|
The set of questions we have defined for the job application is returned from the `QuestionService`.
|
|
In a real app we'd retrieve these questions from storage.
|
|
|
|
The key point is that we control the hero job application questions entirely through the objects returned from `QuestionService`.
|
|
Questionnaire maintenance is a simple matter of adding, updating, and removing objects from the `questions` array.
|
|
|
|
+makeExample('cb-dynamic-form/ts/app/question.service.ts','','app/question.service.ts')
|
|
|
|
:marked
|
|
Finally, we display an instance of the form in the `AppComponent` shell.
|
|
|
|
+makeExample('cb-dynamic-form/ts/app/app.component.ts','','app.component.ts')
|
|
|
|
<a id="dynamic-template"></a>
|
|
:marked
|
|
## Dynamic Template
|
|
Although in this example we're modelling a job application for heroes, there are no references to any specific hero question
|
|
outside the objects returned by `QuestionService`.
|
|
|
|
This is very important since it allows us to repurpose the components for any type of survey
|
|
as long as it's compatible with our *question* object model.
|
|
The key is the dynamic data binding of metadata used to render the form
|
|
without making any hardcoded assumptions about specific questions.
|
|
In addition to control metadata, we are also adding validation dynamically.
|
|
|
|
The *Save* button is disabled until the form is in a valid state.
|
|
When the form is valid, we can click *Save* and the app renders the current form values as JSON.
|
|
This proves that any user input is bound back to the data model.
|
|
Saving and retrieving the data is an exercise for another time.
|
|
|
|
:marked
|
|
The final form looks like this:
|
|
figure.image-display
|
|
img(src="/resources/images/cookbooks/dynamic-form/dynamic-form.png" alt="Dynamic-Form")
|
|
|
|
|
|
:marked
|
|
[Back to top](#top) |