org.javarosa.core.model.condition

Interface IConditionExpr

All Superinterfaces:

Externalizable

All Known Implementing Classes:

XPathConditional

public interface IConditionExpr
extends Externalizable

A condition expression is an expression which is evaluated against the current model and produces a value. These objects should keep track of the expression that they evaluate, as well as being able to identify what references will require the condition to be triggered. As a metaphor into an XForm, a Condition expression represents an XPath expression which you can query for a value (in a calculate or relevancy condition, for instance), can tell you what nodes its value will depend on, and optionally what values it "Pivots" around. (IE: if an expression's value is true if a node is > 25, and false otherwise, it has a "Comparison Pivot" around 25).

Author:

ctsims

Method Summary

Modifier and Type	Method and Description
boolean	eval(DataInstance model, EvaluationContext evalContext) Evaluate this expression against the current models and context and provide a true or false value.
List<TreeReference>	evalNodeset(DataInstance model, EvaluationContext evalContext) Used for itemsets.
Object	evalRaw(DataInstance model, EvaluationContext evalContext) Evaluate this expression against the current models and context and provide the final value of the expression, without forcing a cast to a boolean value.
String	evalReadable(DataInstance model, EvaluationContext evalContext) Used for itemsets.
Set<TreeReference>	getTriggers(TreeReference contextRef) Provides a list of all of the references that this expression's value depends upon directly.
List<Object>	pivot(DataInstance model, EvaluationContext evalContext) Provide a list of Pivots around which this Condition Expression depends.

Methods inherited from interface org.javarosa.core.util.externalizable.Externalizable

readExternal, writeExternal

Method Detail

eval

boolean eval(DataInstance model,
             EvaluationContext evalContext)

Evaluate this expression against the current models and context and provide a true or false value.

Parameters:

model -

evalContext -

Returns:

evalRaw

Object evalRaw(DataInstance model,
               EvaluationContext evalContext)

Evaluate this expression against the current models and context and provide the final value of the expression, without forcing a cast to a boolean value.

Parameters:

model -

evalContext -

Returns:

evalReadable

String evalReadable(DataInstance model,
                    EvaluationContext evalContext)

Used for itemsets. Fill this documentation in.

Parameters:

model -

evalContext -

Returns:

evalNodeset

List<TreeReference> evalNodeset(DataInstance model,
                                EvaluationContext evalContext)

Used for itemsets. Fill this documentation in.

Parameters:

model -

evalContext -

Returns:

getTriggers

Set<TreeReference> getTriggers(TreeReference contextRef)

Provides a list of all of the references that this expression's value depends upon directly. These values can't be contextualized fully (since these triggers are necessary before runtime), but should only need to be contextualized to be a complete set.

Returns:

pivot

List<Object> pivot(DataInstance model,
                   EvaluationContext evalContext)
            throws UnpivotableExpressionException

Provide a list of Pivots around which this Condition Expression depends. Optional to implement. If not implemented, throw an Unpivotable Expression exception to signal that the expression cannot be statically evaluated.

Parameters:

model -

evalContext -

Returns:

Throws:

UnpivotableExpressionException