Condition Class
Represents a boolean expression that is calculated from an AttributeSet.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CECore assembly)
Syntax
public class Condition : ResourceObjectRemarks
Conditions are boolean expressions that are evaluated in the context of an AttributeSet, usually the attributes from a Feature combined with the update attributes from the View.
The most common uses of conditions are to control whether visualizers are applied to certain features or not, to specify which features pass through a FilterOperator and to dynamically turn layers on or off with the Layer.Condition.
Conditions are specified as text strings. In most cases, these are straight-forward, and only test the values of one or two attributes. However, the expressions are quite powerful and can test complex combination of attribute values. For a full description of the expression format, please see Expression Syntax.
The following table shows a few examples of some simple condition strings:
Condition | Description |
|---|---|
a = 5 | True if the attribute set contains an integer or float attribute named a, with a value equal to 5. |
a > 4 and b <= 10 | Assuming the attribute set contains two numeric attributes named a and b, the condition will become true if a is greater than 4 and b is less than or equal to 10. If a or b may be missing from the attribute set, things gets more complex: a missing attribute will evaluate to the special value null that is regarded as less than all other values in comparisons, as described in Expression Syntax. So if a is defined and greater than 4 and b is undefined, the expression will evaluate to true since null is less than 10. But if a is undefined, the expression will evaluate to false since null is not greater than 4. |
a > 4 or a = null | True if the attribute set contains an attribute named a with a value greater than 4, or if the attribute is missing. |
substr(a, 0, 3) = "Foo" | True if the attribute set contains an attribute named a with a string value beginning with Foo. |
If an entire condition expression evaluates to a value of a different type than a bool, it will be regarded as False; no implicit conversion to a bool will be done. (However, some implicit type conversions may be applied to subexpressions of a larger expression; see Expression Syntax.)
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
ResourceObject
Condition
Platforms
Windows, Linux, Android
Condition Members
The Condition type has the following members.
Constructors
| Name | Description |
|---|---|
| Condition | Creates a new Condition. |
Properties
| Name | Description |
|---|---|
| Expression | The boolean expression. |
| IsDisposed | Gets a value that tells whether the current Condition has been disposed. Inherited from EngineObject |
| Name | Gets or sets the name of the Condition. Inherited from ResourceObject |
| NativeHandle | Gets the native Carmenta Engine kernel object the current Condition represents. Inherited from EngineObject |
| IUserProperties.UserProperties | Gets the AttributeSet that contains the user properties. Inherited from IUserProperties |
Methods
| Name | Description |
|---|---|
| Clone | Creates a copy of an object. Inherited from EngineObject |
| Dispose | Releases the reference to the native Carmenta Engine kernel instance the EngineObject represents. Inherited from EngineObject |
| Equals | Determines whether this instance is equal to another. Inherited from EngineObject |
| Evaluate | Evaluates the Condition for the specified AttributeSet. |