I am having a problem saving a domain instance in grails; The domainInstance that's passed to the default update method in my controller is NULL. The GSP page I am submitting from is not the default edit page. I have certain values from DB that need to be saved. I have the form tag defined on the page that contains the values I need to submit, as follows.
<g:form id="sampleForm" url="[resource:domainInstance, controller:'cntrlrName', action:'update']" method="PUT" >
I also have a version field which looks like this.
<g:hiddenField name="version" value="${domainInstance?.version}" />
My g:submit is as follows
<g:actionSubmit action="update" value="${message(code: 'default.button.update.label', default: 'Update')}" />
Why is my domain instance null? What am I missing?
This is the common mistake one could make. The attribute id in <g:form> tag is not the id attribute of HTML tags but it is the id to use in the link for default mapping of Grails i.e.
"/$controller/$action/$id" {}
So change your tag as:
<g:form name="sampleForm" id="${domainInstance.id}" controller="cntrlrName" action="update" method="PUT">
You can pass the domainInstance but I feel it is better practice to pass the id instead of the object. Try passing the id of the domain instance and then reading the object in the controller.
<g:form name="sampleForm" action="action" controller="controller" id="${domainInstance.id}" ></g:form>
// in controller
def resource = Domain.read(params.id)
another approach could be to pass the domainInstance as a hiddenField
<g:hiddenField name="resource" value="$domainInstance" />
Related
Recently I began to study Grails, and I noticed that the file create.groovy is generated by a dynamic scaffold. The form tag doesn't have an attribute called controller, only action.
So my question is, how does the Grails framework discover the controller that should be called?
<g:form action="save">
<fieldset class="form">
<f:field bean="categoria" property="nome" class="form-control" />
</fieldset>
<fieldset class="buttons">
<g:submitButton name="create" class="save" value="${message(code: 'default.button.create.label', default: 'Create')}" />
</fieldset>
</g:form>
Thanks, and sorry for my bad english!
Grails uses "convention over configuration" so whenever you use a form without controller, grails will use the default convention.
Since your view is put in a folder named after a controller, grails will assume that the default controller for any view inside that folder is the one that matches with the folder name. Example
BookController is the default controller for any gsp inside the grails-app/views/book folder.
*This convention also applies to things like links.
As in Struts n JSF, we link a form to a bean(eg. backing bean in JSF).
But in grails, we are using params to set values of the bean. Is there any other way to automatically map a form to the bean?
Grails has the possibility to auto bind values from the params map to a given domain instance / command object. This can be achieved by defining the correct beans as a parameter for your controller methods. Take this example:
Controller:
class AuthorController {
def save(Author author) {
// matching param values are bound to the author instance
assert params.name == "myName"
assert author.name == "myName"
}
}
gsp with form:
<g:form controller="author" action="save">
<g:field name="name" value="myName" />
<g:submitButton name="save" value="Save" />
</g:form>
Sometimes is better to use the Command Objects provided by Grails, the domain class can be wrapped only matching the name of the form fields with the attributes names of the class.
But Command Objects can provide an intermediate layer of validation and abstraction to generate the model bean.
http://grails.org/doc/2.3.0/guide/single.html#commandObjects
The bean class looks like this:
String houseNo
String address
Person person
The view looks like this
<g:form action="save">
<fieldset class="form">
<g:render template="form" />
</fieldset>
<fieldset class="buttons">
<g:submitButton name="create" class="save"
value="${message(code: 'default.button.create.label', default: 'Create')}" />
</fieldset>
</g:form>
According to my knowledge in Grails, i think is <g:render template="form" /> will pull all form attributes and display it.
But what i want to do is Instead of displaying a drop-down for Person, i want to display all Person related fields like personName, personAge. How can i display these fields in a label underneath ?
Help
You're correct about the way g:render works, the template part refers to a GSP which will look through the bean values and print them according to the html + groovy markup in "_form.gsp" (located in your views folder under the controller name).
To change the way the Person domain object is displayed, simply edit this "_form.gsp" and take out the 'select' html code - replacing it with groovy markup using the property values of the bean, eg.
${beanName.person.personName} //(use the existing code to help workout the bean name etc)
Hopefully that helps you on your way.
When you use grails form tag how can you have an id selector in the rendered HTML form tag?
If you use
<g:form action="register" controller="registration" id="registrationform"/>
it renders the form post URL as the /registration/register/registrationform.
Is there a way to provide a property that renders ?
Easiest way is
<g:form action="register" controller="registration" name="registrationForm" />
The name attribute will be used to render the id attribute
You could also use the URL parameter and pass in a map for your action and controller.
<g:form url="[action:'register', controller:'registration']" id="registrationForm" />
How do I get Grails data binding to correctly bind referenced objects (such as Country in the example below)?
Given the following two Grails domain classes ..
class User {
String username
Country country
}
class Country {
String name
}
.. and the following HTML form ..
<g:form>
<g:textField name="user.username" value="${user.username}" />
<g:select name="user.country" from="${Country.list()}" optionKey="id" />
</g:form>
.. and the following code in the corresponding action ..
User user = new User(params["user"])
.. I would have hoped that user.username and user.country would get bind. However, it appears as if username.username gets bind, whereas user.country is not. What is the correct syntax to bind referenced objects (user.country in this example)?
The binding of the "country" property starts working if ..
<g:select name="user.country" from="${Country.list()}" optionKey="id" />
.. is changed to ..
<g:select name="user.country.id" from="${Country.list()}" optionKey="id" />
You should also look into command objects. They can validate and bind all of your parameters at once.