Link
Links within an application represent the relationship between its classes. This section introduces the process of creating a new link, and provides a detailed breakdown of its customization options.
Getting Started
Relationships between classes are defined by creating links in the class designer.
Starting in the Class Designer, click on the down arrow on the left side of the class you wish to work on. Next, expand the Links for the class. Click on Please select to choose the target class for the link. Click on the plus icon on the right of the textbox to create your link.
There are different types of links.
One-To-One Class A can only have one instance of Class B and vice-versa.
One-To-Many Class A has several instances of Class B, but Class B can only be related to a single instance of Class A.
Many-To-Many Class A has several instances of Class B and Class B is related to several instances of Class A as well.
Common Attributes
The Common section contains general properties of a link. In this section, you can specify how the link is presented in your application by setting the name, description and other information.
Key
Currently disabled as this feature is still in development
Parent Link
The parent link is used to specify the inheritance of abstract classes.
Name
The link name is a user-friendly name that is normally generated automatically and set to the target class by default. This value usually does not require modifications.
Description
The description is a short help text that could potentially be used as hover text for the link.
Link Setup
In the Link setup, you can configure the type and specifics of the link between the two classes.
By checking Use Link Service in this section, several aspects of your link is handled by the platform and allows you to have a simpler configuration.
The following options are disabled when Link Service is being used:
NM Class in Common > Link Setup
Controller in Advanced > Advanced
Type in Advanced > Advanced
Normally, Class 1 defines the origin class, while Class 2 defines the target class.
Field 1 identifies the field from Class 1 that should be used as a distinct identifier (foreign key) and normally should be set to the primary key of that class. Similarly, Field 2 specifies the distinct identifier (foreign key) for Class 2 and should be set to the primary key of that class.
Is Source
The source setting defines the direction of a link. By selecting Is Source for a class, you can allow a user to navigate from that class to the other one.
NM Class
When configuring Many-To-Many link types, an extra intermediary table is required to cater for the complex relationship between both classes. The NM Class allows you to specify which table to use from the database. This table will be used to lookup the relations between the linked classes.
Advanced Attributes
In the advanced section of a link, you can further customize the how the link is processed by the platform by linking it to additional code and configuring additional options.
Controller
The controller specifies additional code pertaining to the link that is running in the background.
This setting normally comes preconfigured as Default, which caters for most use cases and should only be modified to accommodate unique scenarios.
Constraint
Link constraints refers to the restriction of links.
For example, Constraints will allow you to define a link as a one-to-many link type, despite having the NM Class - which defines it as a many-to-many link type.
This can be relevant if the target class does not contain a field that can be used to define a normal one-to-many link.
Direction
The link direction can be used to differentiate between two links.
For instance, if a class needs to be linked to itself, you can use Direction to define a parent and child in the link.
Type
The class designer takes care of setting up most properties of your link. However, in this property, you can explicitly define a link type as one-to-many or many-to-many.
However, using the NM Class in the Common Attributes of a link instead can greatly simplify the configuration when creating your classes.
OneToMany
In the link type “OneToMany” a real relationship between one to many instances can be configured.
Type
Yes
The type of link. Must be “OneToMany”.
Class 1
Yes
The One class in One-To-Many. This is usually a main class.
Class 2
Yes
The Many class in One-To-Many. This is usually a dependent class.
Field 1
Yes
The identifying field of class 1 in class 1. This is usually the primary key.
Field 2
Yes
The identifying field of class1 in class 2. This is usually a foreign key.
ManyToMany
In the link type “ManyToMany” a real relationship between many to many instances over a third class can be configured.
Type
Yes
The type of link. Must be “ManyToMany”.
Direction
Yes
The direction of the relation:
None: No specific direction is given.
Children: The direction is from class 1 (left) to class 2 (right).
Parents: The direction is from class 2 (right) to class 1 (left).
Class 1
Yes
The left hand Many class in Many-To-Many. This is usually a main class.
Field 1
Yes
The identifying field of class 1 in class 1. This is usually the primary key.
NM Class
Yes
The relating class in Many-To-Many. This is usually a class only used for the relationship.
NM Field 1
Yes
The identifying field of class 1 in nm class. This is usually a foreign key.
NM Field 2
Yes
The identifying field of class 2 in nm class. This is usually a foreign key.
Class 2
Yes
The right hand Many class in Many-To-Many. This is usually a main class.
Field 2
Yes
The identifying field of class 2 in class 2. This is usually a primary key.
Service
In the link type “ManyToMany” a virtual relationship between many to many instances over a integrated service can be configured.
Type
Yes
The type of link. Must be “Service”.
Class 1
Yes
The left hand Many class in Many-To-Many. This is usually a main class.
Field 1
Yes
The identifying field of class 1 in class 1. This is usually the primary key.
Class 2
Yes
The right hand Many class in Many-To-Many. This is usually a main class.
Field 2
Yes
The identifying field of class 2 in class 2. This is usually a primary key.
Delete Behavior
Class-Designer option to not delete linked instances when deleting an instance. Following delete behavior options are available:
Delete (default): Deletes all linked instances.
Retain: Does not delete linked instances.
Conditions
This feature is still in development at this time.
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