I have a situation that may seem ridiculus but I have not been able to figure out a good enough solution. To simplify things the problem is something like this, suppose you have an object like Manufacturer that has a countryname property (like car.Manufacturer.CountryName) and you want to be sure that the countryname property can not have duplicates or misspellings or other errors.
It is basically a string property but a string can be anything which I do not want. An object seems like overkill and an enum means I have to recompile if new countries are to be added or existing countries to be changed.
I could easily control this in a GUI but I need to control this in the application code. So I have an object with a property that could be a string, an object or an enum (or other) and I cant decide which to use. So my options are something like this:
a) Control this in the GUI and do not check this in the application code, taking the risk that I can get "illegal" country names.
b) Make an object (Country) and use that, which is overkill and makes the code more complex, but I have complete control over duplicates and all that stuff.
c) Use an enum and hope that I do not have to recompile too often. It is simple and effective but a static solution.
d) Use an internal string list of valid country names and have CountryName as a string property and make sure that it is validated against that string. I get validation and CountryName is just a simple string, but what if I change that internal string of valid country names? Than I have to make code the revalidates all Manufacturer objects in the program too make sure they still have valid contry names.
I am not totally sure how important it is too have valid country names but the more I think about this the more I realize that I am in a grey zone. An object, or struct, is too much, an enum too static, a string too simple.
I could be totally overcomplicating things here but I would really like too know what to do, or rather how to think, when you get into this grey zone of object vs string vs enum.
Thankfully yours!
Hal
c) Use an enum and hope that I do not have to recompile too often. It is simple and effective but a static solution.
From this statement I can infer that your data can be subject to change. In these situations, I suggest using an external data store (a database, text file, XML file, whatever).
If country name data integrity is important to you I'd store a list of valid country names in a database or other persistence method, query and cache them inside the application.
Then you can add one post-deployment without recompiling or changing code and with caching you don't incur a lot of overhead for the extra database query.
Go with the object.
It really comes down to a case of do the 'complex' work now and life is easier later on or take the easy route now and life may be more 'complex' later.
Also considering you are actually worried about all the negatives of options b, c & d then just remove your worries!
Also as others have suggested your data should be stored externally to the code (database, xml file etc...) writing an object to wrap this would be your best solution.
I would use a dictionary stored as a separate file, like a XML property list, something like:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist SYSTEM "file://localhost/System/Library/DTDs/PropertyList.dtd">
<plist version="1.0">
<dict>
<key>UK</key>
<string>United Kingdom</string>
<key>FR</key>
<string>France</string>
<key>SP</key>
<string>Spain</string>
</dict>
</plist>
There might be another option:
use a list of Country names stored in an external (possibly human-readable) file. When your program starts, load the country names in an array of strings (or in some other ordered container), and use the order in the list to assign a number to each country (if you use an array, just use the index). A variable containing a country is now just an integer.
Another trick is to use a separate object (which has only one instance) to handle country names. This will ensure that all objects are using the most recent version of the list of country names. Manufacturer objects then do not have a string list, but a reference to the unique object containing the string list.
Related
I have a requirement to display a drop down menu for a String type in Hybris Management Console, restricting the value to some specific values.
As suggested in several forums, I tried to create this entry as an enumeration type but characters like '-' are to be allowed in the enumeration values, as this column receives some specific values which comprise of '-'.
How do I solve this issue?
The people advising you probably didn't understand your requirements. As such, an enumeration type is clearly not appropriate in this case. Consider the alternatives. Is there a Map Type available? What other type might allow you to achieve your goal?
Actually, you could use the hybris Enumeration. In hybris Enum Types have a code and a name. The code is the unique representation for this enum and cannot contain a "-". The name however is a localized representation of that value and can include every character your database is able to store. Have a look here:
https://help.hybris.com/6.5.0/hcd/8c895989866910148d6a802f06651702.html
Additionally, hybris enables you to dynamically create new enumeration values, which is kind of nice.
In a JSF page I have to display the data from an entity.
This entity has some int fields which cannot be displayed directly but need to be translated into a descriptive string.
Between them some can have a limited number of values, others have lots of possible values (such as a wordlwide Country_ID) and deserve a table on the Db with the association (ID, description).
This latter case can easily be solved navigating via relationship from the original entity to the entity corresponding to the dictionary table (ID, description) but I don't want to introduce new entities just to solve translations form ID to description.
Besides another integer field has special needs: the hundred thousand number should be changed with a letter according to a rule such as 100015 -> A00015, 301023 -> C01023.
Initially I put the translation code inside the entity itself but I know the great limits and drawbacks of this solution.
Then I created a singletone (EntityTranslator) with all the methods to translate the different fields. For cases where the field values are a lot I put them inside a table which is loaded from the singletone and transformed in a TreeMap, otherwise the descriptions are in arrays inside the class.
In the ManagedBean I wrote a getter for EntityTranslator and inside the jsf I use quite long el statements like the following:
#{myManagedBean.entityTranslator.translateCountryID(myManagedBean.selectedEntity.countryID)}
I think the problem is quite general and I'm looking for a standard way to solve it but, as already stated, I don't want to create new 'stupid' entities only to associate an ID to a description, I think it is overkill.
Another possibility is the use of converters Object(Integer) <-> String but I'm more comfortable in having all the translation needs for an Entity inside the same class.
Your question boils down to the following simple line:
How can I display a field different from id of my entity in my view and how can I morph an integer field into something more meaningful.
The answer is that it depends on a situation.
If you solely want to input/output data, you don't need id at all apart from the possible view parameter like ?id=12345. In this case you can input/output anything you want in your view: the id is always there.
If you want to create a new entity most possibly you have a way of generating ids via JPA, or database, or elsehow besides the direct input from the user. In this situation you don't need to mess with ids as well.
If you want to use information on other entities like show user a dropdown box with e.g. a list of countries, you always have the option to separate label (let it be name) and value (let it be id), or even have a unique not null column containing the country name in your database table that will serve as a natural identifier. If you'd like to get data from the user using an input text field you always can create a converter that will do the job of transforming user input strings to actual entity objects.
Regarding the transformation of your integers, you've actually got several choices: the first one is to attach a converter for these fields that will roughly do 301023 -> C01023 and C01023 -> 301023 transformations, the second one is to write a custom EL function and the third one is to prepare the right model beforehand / do the transformations on-the-fly.
I need to work with an existing (MySql) db, where the names of tables and columns are already defined.
If I understand the documentation properly (and I didn't find good documentation on this subject, so links will be highly appreciated), table names are related to PersistIdentity, and must therefore begin with a capital letter (which is not the case I'm facing).
Column names, however, are automatically un-capitalized (at least that's what is implied in the Yesod book, Persistent chapter, in the code snippet describing the code automatically generated from declarations), so columns in the DB must begin with a lowercase letter.
Is the description above indeed true?
Can I control specifically the mapping of tables to identities and columns to fields?
If not then what are the rules automatically applied for the naming? What names are therefore forbidden?
Also, one of the fields is a VARCHAR(30). How can I communicate that to Persistent? It currently complains (through yesod devel) that:
errMessage = "BLOB/TEXT column 'my_field' used in key specification without a key length"}
Which is the result of auto-migration (which I probably should disable anyway). However, if I do want to declare a bounded VARCHAR field - can I do that through Persistent and its auto-migration tool?
Thanks,
I'm not an authority on the MySQL backend, but IIRC (and based on the code), you can control the maximum length by using the maxlen=... attribute. Similarly, you can have direct control of the name the field will have in the database by using the sql=... attribute. So, for example, the following might work:
Person sql=people
name Text sql=full_name maxlen=40
age Int
I also agree that you should disable the automigration code if you're dealing with a pre-existing schema.
I am doing a workflow for a document library. I put a OnWorkflowItemChanged, and I want to get the value of the column which is changed. I use the workflowProperties.Item["name"] and use the afterProperties. But when I use the workflowProperties.Item["column name"], I still got the original value. When I use the afterProperties, it's NULL.
Then I make another workflow that is the same as above for a list. I can use the workflowProperties.Item["column name"] to get the new value in OnWorkflowItemChanged.
Has anyone come across this problem before? Can you give me some help?
The question seems to mix up Item with ExtendedProperties. As to why a difference is seen on a List/Document Lib, it might have something to do with versionining or perhaps the internal serialization is different. Anyway, some of my experience is outline below. I hope it may be of use:
Use the GUID (as a Guid object, not a string) to access the Before / After ExtendedProperties field. Using the Display Name in the ExtendedProperties will not work. The documentation on it is wrong. You can use SPList.Fields to go from Display Name to Column ID (Guid).
I bind all "Before" to MyWhatever_PreviousProperties and all "After" to MyWhatever_Properties, only accessing MyWhatever_[Previous]Properties after the appropriate event(s)).
Is there a way to use form fields that does not correspond to database field for temporary processings?
I.e. I want to add:
temp fields item1, item2
database field sum
button with record hook that sets sum = item1 + item2
As far as I know it's simply not possible with ClearQuest.
I've tried to do something similar and was told by our IBM consultant that the only way is to create a DB field for all variables.
You can't attach data to form fields really - those are representations of the underlying data, not something scripts interact with directly.
Adding temporary data to the underlying record (entity) itself sounds unlikely as well. Perhaps it's possible to abuse the perl API and dynamically attach data to entity objects but I personally wouldn't try it, you're liable to lose your data at the whim of CQ then ;-)
That does not however mean it's impossible to have temporary data.
The best way seems to me to be using the session object, which is explicitly intended for that purpose.
From the helpfile:
IBM Rational ClearQuest supports the
use of sessionwide variables for
storing information. After you create
sessionwide variables, you can access
them through the current Session
object using functions or subroutines,
including hooks, that have access to
the Session object. When the current
session ends, all of the variables
associated with that Session object
are deleted. The session ends when the
user logs out or the final reference
to the Session object ceases to exist.
There's some helpful documentation on this subject in file:///C:/Program%20Files/Rational/ClearQuest/doc/help/cq_api/c_session_vars.htm (Presuming a default installation on a windows machine, of course.)
Translating the code example in there into what you seem to be wanting, first you store the data you have calculated inside the session object:
$session->SetNameValue("item1", $value1);
$session->SetNameValue("item2", $value2);
Then in your calculation hook you retrieve the stored values and set the value of that totals field like this:
my $item1 = GetNameValue("item1");
my $item2 = GetNameValue("item2");
my $sum = $item1 + $item2;
$entity->SetFieldValue("some_totals_record", $sum);
Adjust to taste of course ;-)
ClearQuest schema designers often include 'temporary' fields in their record types. They do this so they perform operations on hooks to generate another value.
For example, for the Notes fields, there is a 'temporary' Notes_entry field that the user types the most recent note into, and when the record is saved, the value is added to the Notes_Log field. The next time the record is edited the Notes_entry field is cleared so the user can type a new Notes_entry.