select
目的 Purpose
Generates HTML selects.使用例 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" />
${select(from:aList,value:aValue)}詳細 Description
属性 Attributes
name(required) - The name of the select elementfrom(required) - The list or range to select fromvalue(optional) - The current selected value that evaluates equals() totruefor one of the elements in thefromlist.optionKey(optional) - By defaultvalueattribute of each<option>element will be the result of atoString()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 atoString()call on each element in thefromattribute 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 eachoptionelement.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 objectvalueMessagePrefix(Optional) - By default the value of theoptionelement will be the result of atoString()call on each element in thefromattribute list. Setting this allows the value to be resolved from the i18n messages. ThevalueMessagePrefixwill 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 totrueto generate a multi-select listbox rather than a dropdown list.
optionKey and optionValue attribute of the <g:select> tag deserve special mention as these let you 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}" />
<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}" />
optionKey then be aware that you should use that property in the value attribute in order to pre-select an item in the drop down list. For example, let's say we have a favoriteBook that we want to pre-select in a list of books:<g:select optionKey="id" value="${favoriteBook.id}" name="book" from="${bookList}" />
value should contain the ID of favouriteBook rather than the book object itself because optionKey is set to the id property.