CODEWITHSUNDEEP
persistenceoclmdriven
Kjell Rilbe
Kjell Rilbe

Reputation: 1509

How to use MDriven OclPs to find all objects matching a list of strings?

In an application I receive a list of strings. Then I want to use OclPs to find all objects where a specific attribute equals any of the strings in the list. E.g. if we have Person objects and receive a list of last names, find all persons whose last name appears in the list.

Although this can surely be done in MDriven's in-memory OCL engine, I can't seem to achieve this in the more limited OclPs (which translates the OCL to SQL and evaluates it as such in the database).

Attempt 1: First assign the list of names to vNames (collection of strings), then:

Person.allInstances->select(p|vNames->exists(n|n = p.LastName))

This gives error "Loop variables can only have class type, not System.String".

Attempt 2: First assign a "|" separated string of the sought names, including leading and trailing "|", to vNames, then:

Person.allInstances->select(p|vNames.SqlLike('%|' + p.LastName + '|%'))

This gives error saying strings cant be added in Firebird. But Firebird does support string concatenation using the || operator.

Trying with .Contains(...) instead of .SqlLike(...) says it's not supported in OclPs. Besides, it would find persons with a last name that is CONTAINED in any of the sought names, i.e. an incorrect search.

I'm out of ideas...

Upvotes: 0

Views: 62

Answers (3)

Lars
Lars

Reputation: 201

oclPS only implements a quite small subset of OCL because its converting the OCL to sql.

For example, collections of "non-objects" can't be used.

Person.allInstances->select(p|vNames.SqlLike('%|' + p.LastName + '|%'))

Instead, look at sqlpassthroughobjects here https://wiki.mdriven.net/index.php/OCLOperators_sqlpassthroughobjects

You could also insert the names as objects of a class into the database and then use oclPS.

Upvotes: 1

Hans Karlsen
Hans Karlsen

Reputation: 2435

In this case when you have a long list of strings and you want a list of objects I think you best option is to use SQL with sqlpassthroughobjects:

https://wiki.mdriven.net/index.php/OCLOperators_sqlpassthroughobjects

Person.sqlpassthroughobjects('select personid from person where lastname in ('+vNames->collect(n|'\''+n+'\'')->asCommaList+')')

Upvotes: 1

Ed Willink
Ed Willink

Reputation: 1498

I suggest that you use a genuine OCL tool. You seem to be demonstrating that MDriven OclPs is not OCL.

Upvotes: 0

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