I am getting started with EMF and have completed the EMF tutorial. So far I think I understood the concept. However, I have a class "League" which has a attribute "players" which is a list of Players. I can use the lower and upper bound to restrict the bounds of this list. Lets say I want a league never to have more than 18 Players. I thought setting the upper bound to 18 would do the job. But it does not. I expected the program to throw an exception or not add any more players, when I add more than 18 players.
Or did I understand the upper/lower bounds wrong?
EMF will not throw an exception but it will report a validation error if you validate the root EObject of your model (Resource) using Diagnostician.INSTANCE.validate(yourRootEObject).
Related
Ok, this might take a bit of explanation.
I have a class called PurchaceOrder, which has a form with 18 fields. A lot of the time, there will be several PurchaceOrders with the first 12 fields being the same. To facilitate this (and remove the chance of a user making an error when trying to make the 12 fields the same every time) I have a form that allows the user to add more than one PurchaceOrder with the first 12 Fields being carried over from one entry to the next. This is all fine and good, and is working very well.
However; I need a splash page after the user is done adding all of his/her PurchaceOrders, that shows all the entries that were just made. This means I need to track the new entries that are being created, but I can't think of a way to do this. For now I'm just filtering the categories, so that the PurchaceOrders with the first 12 fields being the same as the ones just entered are displayed, but this obviously won't really work (there could be a previous entry that has those 12 fields that are the same). What I'd really like to have is a list of Primary Keys of the entries that were just created. I could then pass this information onto the view that's responsible for the confirmation landing page.
In my current view I have the following:
if form.is_valid():
entry=form.save()
My thinking was that I could then do something like:
pks = [pks, entry.id]
I don't know where I would instantiate the list. If I did it in the view, it would be whipped out every time the page was reloaded.
I'd appreciate any help.
My first thought would be to have a separate class/method/function that keeps track of the PurchaceOrder's in each form. The ID could be tied to the result through a database or array/linked list that is auto-incremented when a new PurchaceOrder is created.
As far as instantiating the list, have it instantiated when the class is first called, or have it as a separate class. After writing that, a separate class makes more sense, which is probably why I posted it that way originally.
After leaving this alone for a long time, I've finally come up with a suitable solution. What I've done is created a url conf that has a regex of (?P<match>/+)/in it. That rexeg will be used to contain an arbitrary number of primary keys separated by /. I use this to store all of the primary keys of the PurchaseOrders that have been created (that is, when I create PurchaseOrder number 15, it redirects me to /new/15, then when I create number 16, it directs me to /new/15/16/, and so on. Then when I'm ready to confirm, I'm sent to /confirm/15/16/ and I can easily access the pk's of the entries I've just created by calling pks=match.split('/'). I can then simply iterate through pks and do something for each object. I think it's an elegant solution, as long as you don't mind your user seeing the primary keys in the url.
I am having a problem in QTP with selection of a web list box and I have exhausted what I know to do to resolve it. I am hoping someone can help.
There are 5 controls in a container, 2 webedit controls and 3 weblist controls. Together, they allow entry of accounts associated with a customer, and there can be 16 accounts for any customer. There are only ever five controls active at any time, whether editing or entering information for an account. When the information for an account is entered and accepted, it changes to a read-only table row and a new set of controls appears below it for entry of the next account.
The information entered in these controls is the account number, type, description, designation, and status. The status value is contingent on the designation, and the items in the list change dynamically depending on what the user specifies for the designation. The status list is not enabled until the designation is specified.
After some experimenting with timing, I was able to get past an issue where the status list for the first account was seen by QTP as disabled even though it was clearly enabled. I was then able to advance to entry of the second account.
I change the designation on the second account and try to select an appropriate item (specified in a data table) in the status list. My specification from the data table is never found. I figured it was a problem with verbiage differences and also that I should probably anticipate that and address it now, so I wrote a function to accept three parameters, the list and up to two search items. My function searches the listbox passed to it and looks for a match (full or partial) on the search items it receives. Here is where I encountered a significant problem.
The list of the control my function received was from the previous iteration of the test, corresponding to the designation of that account. This is why my function was not finding the selection item. The list on the screen shows the appropriate items, which suggests that I am looking at the wrong object. I also get the ‘object is disabled’ message when I put my data table value directly into the list with the select statement.
The active controls are displayed below the readonly presentation of the previously entered accounts. I am very new to QTP, but I also read documentation. My only theory at this point is that ATP is not passing the right list to my function… that perhaps that how it was learned included the position, which will change each time. However, the spy identifies the screen control as the same item I processed for the preceding account, which makes my theory suspect. In addition, the other four controls, which are not dynamically changing, do not present the same problem. I can put the information in them consistently.
I apologize for the length of this question, but I wanted to be as thorough and clear as possible. Can anyone help me get past this obstacle.
There are many possiblities why it is exposing this behaviour, so let's start with something simple:
Did you try a myWebList.Refresh call before you do something with the listbox? Refresh re-identifies the object.
Have you put a break point (red dot) inside the custom function. Just see what is happening there. With the debug viewer you can enter a realtime command in the scope of that function like msgbox myWebList.exist(0) or myWebList.Highlight
Can you see how the disabled property is propagated to the webpage? If you can 'Object Spy' it as TO property, you can add it in the GUI Map description.
A more sophisticated aproach is to create a Description with the weblist properties. If you can read the disabled property as an RO property from the 'Object Spy', you can use it as an identifier like "attribute/customDisabledProperty:=false".
If you cannot correctly read the disabled property, you can create a description object and do a count on the amount of items that match that description on that page with numberOfLists = Browser("my browser").Page("my page").ChildObjects(myDescription).Count and get the last list with Set lastList = Browser("my browser").Page("my page").ChildObjects(myDescription)(numberOfLists-1)
Keep us informed. Depending on how this works out, we can work into a direction for a solution.
I figured this out early this morning. There are 4 different list boxes used, each made visible or enabled dependent on the selection of the previous list. This is why the spy found the one listed when I was using it and also why the items in the list were not appropriate to what I had selected and also why it appeared disabled to QTP but enabled to me.
I was selecting the same designation when trying to spy it. It was intuitive that the controls were all the same. I am also a windows programmer and I would have populated the same list each time with the appropriate list items, and I presumed that was what the web developer was doing. It was not and it took some time to figure that out. Now that I figured it out, everything is working fine, and I came back to report that. This was a significant, time-intensive lesson.
Thank you very much for your input. It is still useful because I am very new to QTP and every thing I learn is of value.
I am creating a database for an achievement system (like something you would see in a Blizzard game). I would like to have a GUI that displays the current progress of all achievements in the game which means I will need to query the progress of all achievements for a user in order to populate the GUI. I plan on having somewhere around 100 achievements.
This brings about a design question. What is the best way to design the database and querying code to query the progress of ~100 bit fields?
It seems like the brute force method would be to get the entire row of achievements and then for each field in the row do some hardcoded string comparison to determine which achievement we are dealing with.
Another possible solution may be to have a big switch statement based on the column index of the table and handle each achievement for each case (requires not modifying the table or you have to refactor a lot of C++ code).
I'm curious to hear any other designs you guys may have for this.
Thanks!
I suggest building a solution using 3 tables. These tables are users, achievements and user_achievements. A user would be identified with a u_id in the users table. An achievement would be identified with a a_id in the achievements table. You would then keep track of users achievements by inserting a row in the user_achievements table that includes a u_id to identify the user and a a_id to identify the achievement. The user_achievements table would also contain a column that would specify the % completion of that achievement for the given user.
Came across this question and even though it's 5 years old, perhaps someone would be interested in following approach.
Achievements are usually broken down to numbers (the rest, like Name, Description of each achievement can be put to site/app core to avoid bloating the DB).
lets be simple, we are not FB and don't need separate table for them, so in "users" table we add just 1 single column: "Achievements" it is a varchar(50). Number in brackets (50) will depend on your actual needs to this column (i.e. how much data it stores).
so you end up having in each cell of the Achievements column a numerical sequence: 10982039482084109384
Read this line of digits as follows, from left to right: user has reached "1098 profile views", received "2039 likes", etc. Optionally, add a separator for easier distinction + to instantly handle cases when as first user had 25 likes, then 125, then 2039 (2 digits, 3 digits, 4 digits - or another alternative is to use 0025 then 0125 then 2039 given you know max digits is 4 per achievement). But still lets say we decide to use separators, i.e. a comma:
1098,2039,4820,8410,9384
Then once you need a data, just SELECT achievements belonging to specific userID and subsequently (if you added a separator)
explode (',', $array)
then your site php core knows that first 4 digits stand for "profile views" and lets say this means that he has a level 10 badge for profile views (1 badge for 100 views).
Thereon, you can easily do operations with no further need for SQL queries. Example, user wants to know his progress on achieving a level 20 badge, you display: he has a 1098/2000 (or 55%) progress.
At that, achievement Description, Name, level information is stored in site core, while percentage is calculated on the go.
Hope the logic is clear and may be useful to any1 in community out there.
Cheers!
Using Django with a PostgreSQL (8.x) backend, I have a model where I need to skip a block of ids, e.g. after giving out 49999 I want the next id to be 70000 not 50000 (because that block is reserved for another source where the instances are added explicitly with id - I know that's not a great design but it's what I have to work with).
What is the correct/safest place for doing this?
I know I can set the sequence with
SELECT SETVAL(
(SELECT pg_get_serial_sequence('myapp_mymodel', 'id')),
70000,
false
);
but when does Django actually pull a number from the sequence?
Do I override MyModel.save(), call its super and then grab me a cursor and check with
SELECT currval(
(SELECT pg_get_serial_sequence('myapp_mymodel', 'id'))
);
?
I believe that a sequence may be advanced by django even if saving the model fails, so I want to make sure whenever it hits that number it advances - is there a better place than save()?
P.S.: Even if that was the way to go - can I actually figure out the currval for save()'s session like this? if I grab me a connection and cursor, and execute that second SQL statement, wouldn't I be in another session and therefore not get a currval?
Thank you for any pointers.
EDIT: I have a feeling that this must be done at database level (concurrency issues) and posted a corresponding PostgreSQL question - How can I forward a primary key sequence in PostgreSQL safely?
As I haven't found an "automated" way of doing this yet, I'm thinking of the following workaround - it would be feasible for my particular situation:
Set the sequence with a MAXVALUE 49999 NO CYCLE
When 49999 is reached, the next save() will run into a postgres error
Catch that exception and reraise as a form error "you've run out of numbers, please reset to the next block then try again"
Provide a view where the user can activate the next block, i.e. execute "ALTER SEQUENCE my_seq RESTART WITH 70000 MAXVALUE 89999"
I'm uneasy about doing the restart automatically when catching the exception:
try:
instance.save()
except RunOutOfIdsException:
restart_id_sequence()
instance.save()
as I fear two concurrent save()'s running out of ids will lead to two separate restarts, and a subsequent violation of the unique constraint. (basically same concept as original problem)
My next thought was to not use a sequence for the primary key, but rather always specify the id explicitly from a separate counter table which I check/update before using its latest number - that should be safe from concurrency issues. The only problem is that although I have a single place where I add model instances, other parts of django or third-party apps may still rely on an implicit id, which I don't want to break.
But that same mechanism happens to be easily implemented on postgres level - I believe this is the solution:
Don't use SERIAL for the primary key, use DEFAULT my_next_id()
Follow the same logic as for "single level gapless sequence" - http://www.varlena.com/GeneralBits/130.php - my_next_id() does an update followed by a select
Instead of just increasing by 1, check if a boundary was crossed and if so, increase even further
Our C++ program is using Oracle and OCI to do its database work. Occasionally, the user will trigger a constraint violation, which we detect and then show an error message from OCIErrorGet. OCIErrorGet returns strings like this:
ORA-02292: integrity constraint (MYSCHEMA.CC_MYCONSTRAINT) violated - child record found
ORA-06512: at line 5
I am looking for the cleanest way to extract "MYSCHEMA.CC_MYCONSTRAINT" from the Oracle error. Knowing the name of the constraint, I could show a better error message (our code could look up a very meaningful error message if it had access to the constraint name).
I could use a regex or something and assume that the Oracle message will never change, but this seems a little fragile to me. Or I could look for specific ORA codes and then grab whatever text falls between the parentheses. But I was hoping OCI had a cleaner/more robust way, if a constraint fails, to figure out the actual name of the failed constraint without resorting to hardcoded string manipulation.
Any ideas?
According to the Oracle Docs, a string search is exactly what you need to do:
Recognizing Variable Text in Messages
To help you find and fix errors, Oracle embeds object names, numbers,
and character strings in some messages. These embedded variables are
represented by string, number, or character, as appropriate. For
example:
ORA-00020: maximum number of processes (number) exceeded
The preceding message might actually appear as follows:
ORA-00020: maximum number of processes (50) exceeded
Oracle makes a big point in their docs of saying the strings will be kept up to date in their section on "Message Accuracy." It's a pretty strong suggestion that they intend you to do a string search.
Also, according to this website, the Oracle Error structure also pretty strongly implies that they intend you to do a string search, because the data structure lacks anything else for you to get:
array(4) {
["code"]=>int(942)
["message"]=>string(40) "ORA-00942: table or view does not exist"
["offset"]=>int(14)
["sqltext"]=>string(32) "select * from non_existing_table"
}
This output reveals the following information:
The variable $erris an array with four elements.
The first element is accessible by the key ‘code’ and its value is number 942.
The second value is accessible by the key ‘message’ and the value is string “ORA-00942: table or view does not exist”.
The third value is accessible by the key ‘offset’, and its value is the number 14. This is the character before the name of the
non-existing table.
The fourth member is the problematic SQL message causing the error in the first place.
I agree with you; it would be great if there were a better way to get the constraint name you're violating, but string-matching seems to be the intended way.