org.trimou.handlebars

Class AlternativesHelper

java.lang.Object

org.trimou.engine.config.AbstractConfigurationAware

org.trimou.handlebars.AbstractHelper

org.trimou.handlebars.BasicHelper

org.trimou.handlebars.AlternativesHelper

All Implemented Interfaces:

ConfigurationAware, Helper

public class AlternativesHelper
extends BasicHelper

Selects one object from the set of alternatives (usually helper parameters) and:

• for variable - renders its Object.toString() value or if no such object exists renders the output of MissingValueHandler.handle(org.trimou.engine.MustacheTagInfo)
• for section - pushes the object on the context stack or does nothing if no such object exists

If no AlternativesHelper.Selector instance is declared the default behavior is: take the first parameter matching the condition (by default not null or not empty for an instance of String).

In some situations a more appropriate name could be used - the user is free to register this helper with any name - see also MustacheEngineBuilder.registerHelper(String, Helper).

It's useful to specify default values:

Username: {{alt username "Joe"}}

The number of parameters is not limited:

Call me {{alt user.name user.nick "Joe"}}!

A custom AlternativesHelper.Selector might be used to change the default behavior. See for example AlternativesHelper.MinSelector and HelpersBuilder.addMin():

{{min item1.price item2.price}}

Author:

Martin Kouba

See Also:

HelpersBuilder.addAlt()

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AlternativesHelper.ConditionSelector Selects the first parameter matching the condition (by default not null or not empty for an instance of String).
static class	AlternativesHelper.MaxSelector Attempts to select the maximal value from the parameters.
static class	AlternativesHelper.MinSelector Attempts to select the minimal value from the parameters.
static interface	AlternativesHelper.Selector Selects one object from the set of alternatives.

Field Summary

Fields inherited from class org.trimou.handlebars.BasicHelper

HELPER_TAG_TYPES

Fields inherited from class org.trimou.engine.config.AbstractConfigurationAware

configuration

Constructor Summary

Constructors

Constructor and Description
AlternativesHelper() Constructs the default version of the helper using AlternativesHelper.ConditionSelector with the default condition.
AlternativesHelper(AlternativesHelper.Selector selector)

Method Summary

Modifier and Type	Method and Description
void	execute(Options options) Execute the helper.
void	validate(HelperDefinition definition) Helper should validate the tag definition (e.g. number of parameters) during compilation and fail fast if necessary.

Methods inherited from class org.trimou.handlebars.BasicHelper

allowedTagTypes, getRequiredHashKeys, getSupportedHashKeys, numberOfRequiredHashEntries, numberOfRequiredParameters

Methods inherited from class org.trimou.handlebars.AbstractHelper

append, convertAndAppend, convertValue, init, isSection, isUnescapeVariable, isVariable

Methods inherited from class org.trimou.engine.config.AbstractConfigurationAware

checkNotInitialized, init

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.trimou.engine.config.ConfigurationAware

getConfigurationKeys, init

Constructor Detail

AlternativesHelper

public AlternativesHelper()

Constructs the default version of the helper using AlternativesHelper.ConditionSelector with the default condition.

AlternativesHelper

public AlternativesHelper(AlternativesHelper.Selector selector)

Parameters:

selector -

Method Detail

execute

public void execute(Options options)

Description copied from interface: Helper

Execute the helper.

validate

public void validate(HelperDefinition definition)

Description copied from interface: Helper

Helper should validate the tag definition (e.g. number of parameters) during compilation and fail fast if necessary. A MustacheException with code MustacheProblem.COMPILE_HELPER_VALIDATION_FAILURE should be thrown in case of validation failure occurs.

Specified by:

validate in interface Helper

Overrides:

validate in class BasicHelper