Form helpers are designed to make working with resources much easier compared to using vanilla HTML. Typically, a form designed to create or update a resource reflects the identity of the resource in several ways: Input fields are created by calling methods defined on the form builder, which means they are able to generate the appropriate names and default values corresponding to the model attributes, as well as convenient IDs, etc.
Conventions in the generated field names allow controllers to receive form data nicely structured in params with no effort on your side. As you see, the HTML reflects knowledge about the resource in several spots, like the path the form should be submitted to, or the names of the input fields.
In particular, thanks to the conventions followed in the generated field names, the controller gets a nested hash params[: That hash is ready to be passed to Person. Interestingly, the exact same view code in the previous example can be used to edit a person.
ruby on rails odomujekadox.web.fc2.com options with custom attributes - Stack Overflow
Note that the endpoint, default values, and submit button label are tailored for person. That works that way because the involved helpers know whether the resource is a new record or not, and generate HTML accordingly. The controller would receive the form data again in params[: Returns a checkbox tag tailored for accessing a specified attribute identified by method on an object assigned to the template identified by object.
This object must be an instance object object and not a local object. It's intended that method returns an integer and if that integer is above zero, then the checkbox is checked.
Additional options on the input tag can be passed as a hash with options. The HTML specification says unchecked check boxes are not successful, and thus web browsers do not send them. Unfortunately this introduces a gotcha: So, any mass-assignment idiom like.
To prevent this the helper generates an auxiliary hidden field before the very check box. The hidden field has the same name and its attributes mimic an unchecked check box.
This way, the client either sends only the hidden field representing the check box is unchecked , or both fields.
Unfortunately that workaround does not work when the check box goes within an array-like parameter, as in. Scopes input fields with either an explicit scope or model. Fields may reflect a model object in two ways - how they are named hence how submitted values appear within the params hash in the controller and what default values are shown when the form the fields appear in is first displayed.
In order for both of these features to be specified independently, both an object name represented by either a symbol or string and the object itself can be passed to the method separately -.
In this case, the checkbox field will be represented by an HTML input tag with the name attribute permission[admin] , and the submitted value will appear in the controller as params[: This allows you to create forms that set or change the attributes of a parent object and its associations in one go. Nested attribute writers are normal setter methods named after an association.
Whether a one-to-one or one-to-many style form builder will be yielded depends on whether the normal reader method returns a single object or an array of objects.
If you want to destroy the associated model through the form, you have to enable it first using the: If you want to destroy any of the associated models through the form, you have to enable it first using the: When a collection is used you might want to know the index of each object into the array.
For this purpose, the index method is available in the FormBuilder object. Returns a file upload input tag tailored for accessing a specified attribute identified by method on an object assigned to the template identified by object. These options will be tagged onto the HTML as an HTML element attribute as in the example shown. You still need to set up model validations. Creates a form that allows the user to create or update the attributes of a specific model object.
The method can be used in several slightly different ways, depending on how much you wish to rely on Rails to infer automatically from the model how the form should be constructed.
text_field_tag (ActionView::Helpers::FormTagHelper) - APIdock
The variable f yielded to the block is a FormBuilder object that incorporates the knowledge about the model object represented by: Methods defined on the FormBuilder are used to generate fields bound to this model. This means that when the form is submitted, the value entered by the user will be available in the controller as params[: For fields generated in this way using the FormBuilder , if: So for example you may use a named route directly.
When the model is represented by a string or symbol, as in the example above, if the: The namespace attribute will be prefixed with underscore on the generated HTML id.
By default this behavior is an ajax submit. It's still possible to use both the stand-alone FormHelper methods and methods from FormTagHelper. For example, if post is an existing record you wish to edit, you can create the form using. This behaves in almost the same way as outlined previously, with a couple of small exceptions. First, the prefix used to name the input elements within the form hence the key that denotes them in the params hash is actually derived from the object's class , e.
However, this can be overwritten using the: So, for example, if we had a local variable post representing an existing record,. In the examples just shown, although not indicated explicitly, we still need to use the: In this case Rails will simply infer the appropriate URL from the record itself. If your resource has associations defined, for example, you want to add comments to the document given that the routes are set correctly:.
This is used to maintain the correlation between the form data and its associated model. Some ORM systems do not use IDs on nested models so in this case you want to be able to disable the hidden id. In the following example the Post model has many Comments stored within it in a NoSQL database, thus there is no primary key for comments.
You can also build forms using a customized FormBuilder class. Subclass FormBuilder and override or define some more helpers, then use your custom builder. For example, let's say you made a helper to automatically add labels to form inputs.
In many cases you will want to wrap the above in another helper, so you could do something like the following:. If you don't need to attach a form to a model instance, then check out ActionView:: When you build forms to external resources sometimes you need to set an authenticity token or just render a form without it, for example when you submit data to a payment gateway number and types of fields could be limited.
If you don't want to an authenticity token field be rendered at all just pass false:. The parameters in the forms are accessible in controllers according to their name nesting. So inputs named title and post[title] are accessible as params[: For ease of comparison the examples above left out the submit button, as well as the auto generated hidden fields that enable UTF-8 support and adds an authenticity token needed for cross site request forgery protection.
For example, you may use a named route directly. Useful when submitting to another resource type, like: If the model is a new record a create form is generated, if an existing record, however, an update form is generated. Override with a custom authenticity token or pass false to skip the authenticity token field altogether. Useful when submitting to an external resource like a payment gateway that might limit the valid fields.
This is helpful when fragment-caching the form. Disable remote submits with local: Set to true to skip the field. You can set data attributes directly in a data hash, but HTML options besides id and class must be wrapped in an HTML key:. The custom FormBuilder class is automatically merged with the options of a nested fields call, unless it's explicitly set.
Returns a hidden input tag tailored for accessing a specified attribute identified by method on an object assigned to the template identified by object. Returns a label tag tailored for labelling an input field for a specified attribute identified by method on an object assigned to the template identified by object. The text of label will default to the attribute name unless a translation is found in the current I18n locale through helpers.
Additional options on the label tag can be passed as a hash with options. These options will be tagged onto the HTML as an HTML element attribute as in the example shown, except for the: You can localize your labels based on model and attribute names. For example you can define the following in your locale e. Localization can also be based purely on the translation of the attribute-name if you are using ActiveRecord:.
For security reasons this field is blank by default; pass in a value via options if this is not desired. Returns a radio button tag for accessing a specified attribute identified by method on an object assigned to the template identified by object.
To force the radio button to be checked pass checked: You may pass HTML options there as well. Returns a textarea opening and closing tag set tailored for accessing a specified attribute identified by method on an object assigned to the template identified by object.
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Gotcha The HTML specification says unchecked check boxes are not successful, and thus web browsers do not send them. So, any mass-assignment idiom like invoice. Let's say that post. Using a scope prefixes the input field names: When using labels fields requires setting the id on the field being labelled: Options Creates standard HTML attributes for the tag.
Resource-oriented style In the examples just shown, although not indicated explicitly, we still need to use the: Setting the method You can force the form to use the full array of HTTP verbs by setting method: In many cases you will want to wrap the above in another helper, so you could do something like the following: Form to external resources When you build forms to external resources sometimes you need to set an authenticity token or just render a form without it, for example when you submit data to a payment gateway number and types of fields could be limited.
To set an authenticity token you need to pass an: Creates a form tag based on mixing URLs, scopes, or models. Using just a URL: Setting HTML options You can set data attributes directly in a data hash, but HTML options besides id and class must be wrapped in an HTML key: