[Type] Collection
Part of: mobl
Inherits from: mobl::Object
A Collection represents a (often) virtual collection of items. These collections can be filtered, sorted and truncated.
Syntactic sugar
There is a nicer, more SQL syntax that translates down to the methods defined below. The syntax in BNF-like format looks as follows:
Exp ::= Exp Filter+
Filter ::= "where" SetExp
Filter ::= "order" "by" OrderExp
Filter ::= "prefetch" {ID ","}+
Filter ::= "limit" Exp
Filter ::= "offset" Exp
SetExp ::= ID "==" Exp
| ID "!=" Exp
| ID "<" Exp
| ID "<=" Exp
| ID ">" Exp
| ID "in" Exp
| ID "not" "in" Exp
OrderExp ::= ID | ID "asc" | ID "desc"
Example:
var coll = Task.all() where done == true
order by date desc
prefetch category
limit 10
skip 10;
Instantiation
A new Collection can be created by using the Collection<T>() constructor.
Example:
var coll = Collection<Task>();
Instance methods
one() : T
Returns one element of the collection (or null if the collection is empty).
Example:
var oneTask = Task.all().one()
prefetch(property : String) : Collection<T>
Returns a new collection that prefetches the given property. In effect performs a join with the property's table (only works for reference properties).
Example:
list(t in Task.all().prefetch("category")) {
"[" label(t.category.name) "]"
label(t.name)
}
filter(property : String, op : String, value : Object) : Collection<T>
Returns a new collection that filters based on a property. Supported
operators are: =, !=, <, >, <=, >=, in and not in.
Example:
var coll = Task.all().filter("done", "=", true);
order(property : String, ascending : Bool) : Collection<T>
Returns a new collection that is sorted based on a property in either
ascending (ascending is true) or descending (ascending is
false).
Example:
var coll = Task.all().order("date", false);
reverse() : Collection<T>
Returns a new collection that reverses its result set.
Example:
var coll = Task.all().order("date", true).reverse();
destroyAll() : void
Removes all elements in the collection from the database.
Example:
Task.all().filter("date", "<", old).destroyAll();
count() : Num
Returns the number of items in the collection.
Example:
Task.all().count()
list() : Array<T>
Turns the collection into an array.
Example:
var ar = Task.all().list()
selectJSON(properties : [String]) : JSON
Returns a JSON representation of a subset of a collection. The properties argument expects an array with property names. Some examples:
["id", "name"], will return an object with the id and name property of this entity["*"], will return an object with all the properties of this entity, not recursive["project.name"], will return an object with a project property which has a name property containing the project name (hasOne relationship)["project.[id, name]"], will return an object with a project property which has an id and name property containing the project name (hasOne relationship)["tags.name"], will return an object with an array tags property containing objects each with a single property: name
limit(n : Num) : Collection<T>
Returns a collection that limits the number of results to n.
Example:
Task.all().limit(10)
skip(n : Num) : Collection<T>
Returns a collection that skips the first n elements, for instance to implement paging.
Example:
Task.all().limit(10).skip(10) // page 2
add(item : T) : void
Adds item item to the collection.
Example:
coll.add(Task(name="Groceries"));
remove(item : T) : void
Removes item item from the collection (but does not remove the item itself).
Example:
coll.remove(t);