Package com.inductiveautomation.ignition.common.expressions

Interface Expression

All Known Implementing Classes:
AbstractAlertExpressionContext.AlertVariableExpression, AbstractExpression, AlarmEventPropertyExpression, ArithmeticExpression, BitwiseExpression, BitwiseNot, BoundPropertyExpression, BoundPropertyExpression, BoundTagExpression, BoundVariableExpression, ComparisonExpression, ConstantExpression, EqualityExpression, FormattedExpression, FunctionExpression, LikeExpression, LocaleAwareMessageParseContext.LocaleStringExpression, LogicalExpression, NonLocalizedToStringExpression, NotExpression, PropertyBasedExpressionParseContext.PropertyReferenceExpression, SubscriptExpression, TagPathReadExpression, TagReferenceBinder.SubscribedTagExpression, TagReferenceBinder.TagReadExpression, ToStringExpression, UMinusExpression
public interface Expression
An expression is something that can be executed to compute a result. Each instance of expression is typically some node in what amounts to a parse tree. Many expressions such as operators and function calls have child expressions.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    connect(CommonContext context, InteractionListener updateListener)
    Gives the expression a chance to connect itself to things, if necessary.
    void
    disconnect()
    Tells the expression to disconnect from anything it was connected to.
    QualifiedValue
    execute()
    Compute and return the value of this expression
    Expression[]
    getChildren()
    The children (if any) that this expression is dependent on for its execution
    String
    getOpName()
    Return a human-readable name for the operation that this expression performs
    default Class<?>
    getType()
    Return the type that this expression will return
    void
    shutdown()
    Tells the expression to shutdown any polling operations.
    void
    startup()
    Tells the expression to startup any polling operations.

  • Method Details

    • execute

      @Nonnull QualifiedValue execute() throws ExpressionException
      Compute and return the value of this expression
      Throws:
      ExpressionException

    • getType

      default Class<?> getType()
      Return the type that this expression will return

    • getOpName

      String getOpName()
      Return a human-readable name for the operation that this expression performs

    • getChildren

      Expression[] getChildren()
      The children (if any) that this expression is dependent on for its execution

    • connect

      void connect(CommonContext context, InteractionListener updateListener)
      Gives the expression a chance to connect itself to things, if necessary. Most expressions do not have any connections. An expression should notify the updateListener if they change.

    • disconnect

      void disconnect()
      Tells the expression to disconnect from anything it was connected to.

    • startup

      void startup()
      Tells the expression to startup any polling operations. Expressions that use this can remember the updateListener from connect() to feed update notification to.

    • shutdown

      void shutdown()
      Tells the expression to shutdown any polling operations.