In our previous posts in this series, we talked about how an MboSet is a collection of Mbo objects. This is analogous to a spreadsheet of data representing an MboSet, and a single row within that spreadsheet representing an Mbo. This article will discuss how to work with records related to an Mbo or MboSet.
All examples so far in this series have dealt with individual objects. It is possible to use an object as a starting point for traversing to other objects that are related in some way to retrieve, for example, the planned labor or the asset associated with a work order. There are two possible approaches to achieve this. The more general one is to use the getMboSet() method of a Mbo as shown in the following examples.
# Get the planned labor objects associated with the work order
wpLaborSet = mbo.getMboSet("WPLABOR")
wpLaborCount = wpLaborSet.count()
# Get the associated asset along with some of its data
assetList = mbo.getMboSet("ASSET")
asset = assetList.moveFirst()
serialNumber = asset.getString("SERIALNUM")
The mbo.getMboSet(“WPLABOR”) method call above returns a collection of WPLabor objects, specifically, those labor requirements associated with the first work order on the current work order Mbo. There is a 1:N relationship between work orders and Work Plan Labor objects as a given work order may have multiple labor requirements associated with it. Thus, the wpLaborSet may have from 1 to N members. Note that wpLaborSet is a standard MboSet object, containing all the standard member methods, any of which may be called in the standard way.
In some cases, related objects are in a 1:1 relationship such as work order to asset (mostly… except in multi-asset cases). A given work order only has one asset associated with it at a time in most cases. Thus, when getMboSet(“ASSET”) is called on a work order, the returned MboSet will contains a single object if the ASSETNUM field is populated on the work order.
A list of objects with relationships to other objects (including the relationship name, which is the argument to be passed to the getMboSet() method, the type of objects in the returned MboSet, and the nature of the numerical relationship, i.e. 1:N vs. 1:1) is provided in the Relationships tab of the Database Configuration application in Maximo.
The second approach to working with associated objects amounts to a shortcut which can be used when only the data value of some attribute of a related object is needed. This approach is referred to as “dot notation” and it allows the retrieval of an object’s data without retrieving the object itself. It is most convenient in cases where the relationship is of the 1:1 type. While it does work for 1:N relationships, its usefulness is somewhat restricted.
The following code illustrates how the dot notation is used:
woSet = mbo.getMboSet("WORKORDER")
wo = woSet.getMbo(0)
serialNumber = wo.getString("ASSET.SERIALNUM")
assetLongDescription = wo.getString("ASSET.DESCRIPTION_LONGDESCRIPTION")
problemDescription = wo.getString("PROBLEM.DESCRIPTION")
Dot notation is therefore a call to a WO’s (or, more generally, a Mbo’s) getString() method with a special argument. The argument has two parts, separated by the dot. The first is the relationship name; the second is the name of the associated object’s attribute whose value is being retrieved. Please note that relationships can also be chained together using more than two parts (e.g. “LABOR.PERSON.DISPLAYNAME”), however the majority of cases will be two strings separated by a dot. It’s also important to note that the relationship name is just that; oftentimes Maximo uses the object name itself as the relationship name, but in some cases the relationship name is different than the object name. This is especially true where one object relates to another object via multiple fields (e.g. CHANGEBY and REPORTEDBY both refer to the PERSON object, therefore two different relationship names are needed to distinguish the PERSON.DISPLAYNAME field as the values may be different).
The first part in the above example retrieves a reference to a specific WO object. The next three lines call its getString() method with different examples of the dot notation. The call to wo.getString(“ASSET.SERIALNUM”) retrieves the value of the serialNum attribute for the associated Asset object. This line achieves the same result as in the general example at the start of this article but without accessing the Asset object itself at all.
The call to wo.getString(“ASSET.DESCRIPTION_LONGDESCRIPTION”) illustrates how the dot notation also works for more unusual attributes like long descriptions.
The call to wo.getString(“PROBLEM.DESCRIPTION”) is a somewhat more complicated example. The relationship name is “problem”, but the type of associated object being accessed is not a hypothetical “Problem” object (which in fact does not exist) but rather a Failure object. Thus, the “description” attribute being specified is actually the “description” attribute of a Failure object (specifically, that Failure object specified by the value in the WO object’s “problemcode” attribute). This example illustrates how the dot notation can be used even when the relationship name is different from the name of the associated object.
If the dot notation is used when the relationship is 1:N then the data value of the first object’s attribute is returned. This can be a serious limitation since there is no guarantee as to which associated object is the first one. The only way to find out is to check explicitly.
If the dot notation is used in a case where there is no associated object, e.g. if the “ASSET.SERIALNUM” is requested for a work order which has no Asset associated with it, an MxApplicationException is thrown.