I have a Grails domain called People, and I want to check that each People has childs or not. Childs are other People objects. Here is my domain structure:
class People implements Serializable {
static constraints = {
name (nullable : false, unique : true)
createdBy (nullable : false)
creationDate (nullable : false)
}
static transients = ['hasChild']
static mapping = {
table 'PEOPLE'
id generator: 'sequence', params : [sequence : 'SEQ_PK_ID']
columns {
id column : 'APEOPLE_ID'
parentPeople column : 'PARENT_PEOPLE_ID'
}
parentPeople lazy : false
}
People parentPeople
String name
String description
Boolean hasChild() {
def childPeoples = People.createCriteria().count {
eq ('parentPeople', People)
}
return (childPeoples > 0)
}
}
But I cannot call people.hasChild() at anywhere. Could you please helpe me on this? Thank you so much!
It's because in eq ('parentPeople', People), Grails can't understand what "People" is (it's a class). You should replace "People" by this. For example:
static transients = ["children"]
def getChildren() {
def childPeoples = People.findAllByParentPeople(this, [sort:'id',order:'asc'])
}
Another way to get the same result is to use Named Queries. It seems more concise and was created specifically for this purpose. I also like it because it fits the pattern of static declarations in a domain model and it's essentially a criteria, which I use throughout my applications. Declaring a transient then writing a closure seems a bit of a work-around when you can declare named queries ... just my opinion.
Try something like this:
static namedQueries = {
getChildren {
projections {
count "parentPeople"
}
}
}
Related
class Client {
String name
static hasMany = [courses:Course]
}
class Course {
String name
static belongsTo = [client:Client]
}
I have this and I want to get all Clients that has a Course with name = "blabla"
I was trying to do : Clients.findWhere(Course.any { course -> course.name = "math" })
You can do this with criteria:
Client.withCriteria {
courses {
eq('name', 'math')
}
}
I believe that the following where query is equivalent to the above criteria:
Client.where { courses.name == 'math' }
or you may find you need another closure:
Client.where {
courses {
name == 'math'
}
}
but I rarely use where queries myself so I'm not 100% sure of that.
There are probably a lot of different syntactical expressions to achieve the same thing. I can say definitively that this works in my project though.
def ls = Client.list {
courses {
eq('name','math')
}
}
I read that a m:m relationship often means there is a third class that isn't yet required. So I have m:m on User and Project, and I created a third domain class, ProjectMembership
The three domains are as follows (minimized for illustration purposes):
User
class User {
String name
static hasMany = [projectMemberships : ProjectMembership]
}
Project Membership
class ProjectMembership {
static constraints = {
}
static belongsTo = [user:User, project:Project]
}
Project:
class Project {
String name
static hasMany = [projectMemberships : ProjectMembership]
static constraints = {
}
}
If I have the ID of the user, how can I get a list of Project objects that they are assigned to?
There are a handful of ways - here are a couple:
def user = User.get(userId)
ProjectMembership.findAllByUser(user).collect { it.project }
or to avoid the query for the User:
ProjectMembership.withCriteria {
user {
eq('id', userId)
}
}.collect { it.project }
Be wary of queries that'll return large result sets - you'll end up with a huge in-memory list of project objects.
I've got a grails domain class I have to persist in Redis, something like this:
class A {
String one
Integer two
B three
E four
mapWith = "redis"
}
class B {
String name
}
enum E {
VALUE1, VALUE2
}
When I persist an instance of class A with the GORM .save() method, Redis saves it correctly except for the enum field "four".
As you can see the fact is known and reported here: http://jira.grails.org/browse/GPREDIS-3
Is there a good workaround to save Enum or something similar?
We're thinking about an array of String objects, what do you think?
I've got this mostly implemented but it doesn't work for Gemfire and I'm waiting until it's fixed for all the supported nosql providers before pushing the fix. As a workaround you can use the inList constraint with a combination of a persistent String property and a non-persistent get/set pair with the name of your current property, e.g.
class A {
String one
Integer two
B three
String fourString
void setFour(E e) {
fourString = e?.name()
}
E getFour() {
fourString ? E.valueOf(fourString) : null
}
static constraints = {
fourString inList: E.values()*.name()
}
static transients = ['fourString']
static mapWith = "redis"
}
I'm writing some named queries for my domain classes in Grails and I've hit a blocker.
Given the following domain class:
class Contributor {
// evals is a collection of another domain class
def evals
static namedQueries = {
hasNoEvals {
// Something like this...
evals.size() == 0
}
}
}
Can anyone help with the syntax I need to select the Contributors who have no Evals?
Thanks.
Please look in createCriteria doc for "collection property" operations. In your case, it is isEmpty:
static namedQueries = {
hasNoEvals {
isEmpty('evals')
}
}
For generic size restriction, it is sizeEq, sizeLe and so on.
in my domain model, I have a method that does something with my data.
e.g.
class Person {
String lastname
String firstname
String bigname() {
return lastname.toUpperCase()
}
static namedQueries = {
withBigname { name ->
eq(this.bigname(), name)
}
}
}
I want to use this method like a property in the named query, but this.bigname() only throws a java.lang.IncompatibleClassChangeError-Exception.
Does anyone know how to use domain methods in criteria and named queries?
Update: I now tried this:
class Person {
String lastname
String firstname
String bigname
static transients = [ 'bigname' ]
def getBigname() {
return lastname.toUpperCase()
}
static namedQueries = {
withBigname { name ->
eq('bigname', name)
}
}
}
But it only results in a "could not resolve property: bigname"-exception...
You cannot use class methods in queries, because queries are actually translated to SQL.
You might be able to get what you need by using writing the complexity in SQL a "SQL Restriction". Search for "SQL Restriction" on http://grails.org/doc/2.0.x/guide/GORM.html
HTH
Try to name the method in JavaBean getter and setter notation.
Rename method bigname() to getBigname().
On a static closure, you don't have a this. You'll either need to store the bigname in the Database, do some sort of case insensitive criteria.
looks like you are trying to accomplish this:
class Person {
String lastname
String firstname
static namedQueries = {
withName { name ->
eq('lastname', name, [ignoreCase: true])
}
}
}