(Quick Reference)

select

Purpose

Helper tag for creating HTML selects.

Examples

// create a select from a range
<g:select name="user.age" from="${18..65}" value="${age}"
          noSelection="['':'-Choose your age-']"/>

// use a no selection with a nullable Object property (use 'null' as key) <g:select id="type" name='type.id' value="${person?.type?.id}" noSelection="${['null':'Select One...']}" from='${PersonType.list()}' optionKey="id" optionValue="name"></g:select>

// create select from a list of companies // note the 'optionKey' is set to the id of each company element <g:select name="user.company.id" from="${Company.list()}" value="${user?.company.id}" optionKey="id" />

// create multiple select <g:select name="cars" from="${Car.list()}" value="${person?.cars*.id}" optionKey="id" multiple="true" />

// create select with internationalized labels (this is useful for small static lists and the inList constraint) // expected properties in messages.properties: // book.category.M=Mystery // book.category.T=Thriller // book.category.F=Fantasy <g:select name="book.category" from="${['M', 'T', 'F']}" valueMessagePrefix="book.category" />

Example as a method call in GSP only:

${select(from:aList,value:aValue)}

Description

Attributes

  • from (required) - The list or range to select from
  • value (optional) - The current selected value that evaluates equals() to true for one of the elements in the from list.
  • optionKey (optional) - By default value attribute of each <option> element will be the result of a "toString()" call on each element. Setting this allows the value to be a bean property of each element in the list.
  • optionValue (optional) - By default the body of each <option> element will be the result of a "toString()" call on each element in the "from" attribute list. Setting this allows the value to be a bean property of each element in the list.
  • keys (optional) - A list of values to be used for the value attribute of each "option" element.
  • noSelection (optional) - A single-entry map detailing the key and value to use for the "no selection made" choice in the select box. If there is no current selection this will be shown as it is first in the list, and if submitted with this selected, the key that you provide will be submitted. Typically this will be blank - but you can also use 'null' in the case that you're passing the ID of an object
  • valueMessagePrefix (Optional) - By default the value "option" element will be the result of a "toString()" call on each element in the "from" attribute list. Setting this allows the value to be resolved from the I18n messages. The valueMessagePrefix will be suffixed with a dot ('.') and then the value attribute of the option to resolve the message. If the message could not be resolved, the value is presented.
  • multiple (optional) - Set to "true" to generate a multi-select listbox rather than a dropdown list.

The optionKey and optionValue attribute of the <g:select> tag deserve special mention as these allow you to control what is displayed to the user within the resulting <select> tag and also the value which is submitted in a form submission. The default behaviour is to call toString() on each element in the from attribute, but for example if you had a list of Book domain classes this may not be useful behaviour.

As an example the following <g:select> uses the optionKey attribute to resolve the id property of each Book as the value of the value attribute in each <option> tag. It also uses the optionValue attribute of <g:select> to display the title property of each Book to the user:

<g:select optionKey="id" optionValue="title" name="book.title" from="${bookList}" />

If you require even more control over how each <option> element is presented to the user you can use a closure to apply a transformation within the optionValue attribute. As an example, the following code transforms each Book title to upper case:

<g:select optionKey="id" optionValue="${{it.title?.toUpperCase()}}" name="book.title" from="${bookList}" />

Source

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