ESInputTag Class Reference

#include <FWCore/Utilities/interface/ESInputTag.h>

Detailed Description

Description: Parameter type used to denote how data should be obtained from the EventSetup

Usage: The ESInputTag can be used in conjunction with an EventSetup Record to retrieve a particular data item from the Record. The EventSetup uses two pieces of information to find data in a Record 1) the C++ class type of the data 2) an optional string which we will refer to as the 'dataLabel' The dataLabel is used to differentiate objects of the same type placed in the same Record.

In addition, every piece of data in the EventSetup comes from either an ESSource or an ESProducer. Every ESSource and ESProducer is assigned a label (referred to here as the moduleLabel) in the configuration of the job. This label may be explicitly set or it may just be the C++ class type of the ESSource/ESProducer. For example, say there is an ESProducer of C++ class type FooESProd. If the python configuration has process.FooESProd = cms.ESProducer("FooESProd", ...) then the module label is 'FooESProd'. If the python configuration has process.add_( cms.ESProducer("FooESProd", ...) then the module label is also 'FooESProd'. However, if the python configuration has process.foos = cms.ESProducer("FooESProd",...) then the module label is 'foos'.

The ESInputTag allows one to specify both the dataLabel and moduleLabel. The dataLabel is used to find the data being requested. The moduleLabel is only used to determine if the data that was found comes from the specified module. If the data does not come from the module then an error has occurred. If the moduleLabel is set to the empty string then the data is allowed to come from any module.

Example 1: FooESProd makes Foos with the default dataLabel ("") The module is declared in the python configuration as process.FooESProd = cms.ESProducer("FooESProd",...) The following python configurations for ESInputTag can be used to get its data cms.ESInputTag("") cms.ESInputTag(":") cms.ESInputTag("","") cms.ESInputTag("FooESProd") cms.ESInputTag("FooESProd:") cms.ESInputTag("FooESProd","")

Example 2: FooESProd makes Foos with the dataLabel "bar" The module is declared in the python configuration as process.FooESProd = cms.ESProducer("FooESProd",...) The following python configurations for ESInputTag can be used to get its data cms.ESInputTag(":bar") cms.ESInputTag("","bar") cms.ESInputTag("FooESProd:bar") cms.ESInputTag("FooESProd","bar")

Example 3: FooESProd makes Foos with the default dataLabel ("") process.FooESProd = cms.ESProducer("FooESProd",...) Foo2ESProd also makes Foos with the default dataLabel ("") process.Foo2ESProd = cms.ESProducer("Foo2ESProd",...) The jobs has an ESPrefer which states Foos should come from FooESProd process.perferedFoo = cms.ESPrefer("FooESProd") Then to get the data, one can specify the ESInputTag identical to Example 1. However, the following ESInputTags will lead to an exception begin thrown cms.ESInputTag("Foo2ESProd") cms.ESInputTag("Foo2ESProd:") cms.ESInputTag("Foo2ESProd","") The exception happens because FooESProd is the only allowed source of Foos but the ESInputTag says you really wanted them to come from Foo2ESProd.