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Merge pull request #2223 from tractorcow/3.1-belongs_to-docs

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Documentation for belongs_to
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Ingo Schommer 2013-08-29 16:34:37 -07:00
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docs/en/topics/datamodel.md
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@ -584,6 +584,35 @@ object type.
}
### belongs_to
Defines a 1-to-1 relationship with another object, which declares the other end
of the relationship with a corresponding $has_one. A single database column named
`<relationship-name>ID` will be created in the object with the $has_one, but
the $belongs_to by itself will not create a database field. This field will hold
the ID of the object declaring the $belongs_to.
Similarly with $has_many, dot notation can be used to explicitly specify the $has_one
which refers to this relation. This is not mandatory unless the relationship would
be otherwise ambiguous.
:::php
class Torso extends DataObject {
// HeadID will be generated on the Torso table
private static $has_one = array(
'Head' => 'Head'
);
}
class Head extends DataObject {
// No database field created. The '.Head' suffix could be omitted
private static $belongs_to = array(
'Torso' => 'Torso.Head'
);
}
### many_many
Defines many-to-many joins. A new table, (this-class)_(relationship-name), will