Grails findAll Tag Examples

Mar 09, 2015 Tag comments

This will show examples on how to use the Grails findAll tag(<g:findAll>). This tag is similar to each tag and uses the Groovy JDK findAll method to iterate over each element of a collection and only renders the body if the attribute "expr" is evaluated to true.

Test Data

For the examples, we assume that we have this domain class

class Person {
    String firstName
    String lastName
    int age
}

And this inserted data:

class BootStrap {
    def init = { servletContext ->
        if (Person.count()==0) {
            new Person(firstName: 'John', lastName: 'Doe', age: 10).save()
            new Person(firstName: 'Jane', lastName: 'Doe', age: 10).save()
            new Person(firstName: 'Jesse', lastName: 'Doe', age: 10).save()
            new Person(firstName: 'Rex', lastName: 'Smith', age: 12).save()
            new Person(firstName: 'Roy', lastName: 'Smith', age: 12).save()
            new Person(firstName: 'Amy', lastName: 'Johnson', age: 8).save()
        }
    }
}

And this controller code that returns all records in the Person domain class:

class PersonController {
    def list() {
        [people:Person.listOrderByLastName()]
    }
}

Required attributes: in and expr

By default, in and expr attributes are required when using Grails findAll tag.

in - the list or collection to iterate over
expr - a logical expression that should evaluate to either true or false

Here is a quick example:

<g:findAll in="${people}" expr="true">
    <p>${it.lastName}, ${it.firstName}</p>
</g:findAll>

Since the expr is always evaluated to true, this will in fact render the body over all the items of the list. The output will be this:

Doe, John
Doe, Jane
Doe, Jesse
Johnson, Amy
Smith, Rex
Smith, Roy

We can change the expr to something meaningful for our Grails findAll tag code to process:

<g:findAll in="${people}" expr="it.lastName == 'Doe'">
    <p>${it.lastName}, ${it.firstName}</p>
</g:findAll>

This will only execute the body when lastName is Doe. Hence, this is the expected result:

Doe, John
Doe, Jane
Doe, Jesse

Here is another sample that only process records for people who has age greater than 10.

<g:findAll in="${people}" expr=" ${it.age > 10} ">
    <p>${it.lastName}, ${it.firstName}</p>
</g:findAll>

Notice that we can enclose our expression inside ${}. Here is the expected output:

Smith, Rex
Smith, Roy

Attributes: var

For readability, we can specify the var attribute. This will replace the it in our inner expressions. Here is a findAll tag example:

<g:findAll in="${people}" expr="${it.age == 10}" var="person">
    <p>${person.lastName}, ${person.firstName}</p>
</g:findAll>

The code will display these records:

Doe, John
Doe, Jane
Doe, Jesse

Specifying the var attribute makes the Grails findAll tag code easy to read at quick glance because of the logical variable name.

Attributes: status

The status attribute can be specified also. This will be the variable name that holds the index of the current element. Here is an example:

<g:findAll in="${people}" expr="${it.age == 10}" var="person" status="ctr">
    <p>${ctr+1}. ${person.lastName}, ${person.firstName}</p>
</g:findAll>

The code will display this output. As you can see, the index is zero-based - meaning it will start from the value 0. Hence we add 1 to the number before rendering:

1. Doe, John
2. Doe, Jane
3. Doe, Jesse

Other Grails Tag Examples

Tags: findAll, Grails Tag

Beginners Tutorial

Example Applications

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