| Hi and welcome back to MDriven designer overview and this will be session five, so we ended off the last session with the creating a modal dialog that were allowed us to pick tenants to our house so we could pick persons that would create lease contract and when we used this dialogue "all persons" to to pick the tenants from and as you can imagine this strategy simply will not hold, if we have a million persons and this is good, when we have a hundred maybe, but we can't really trust on all instances to come to the rescue for every scenario, we really desperately need some way to vSeek the database without instanciating the objects in memory in their client during the prototyper, so how do we go about that in the view model pattern that we have we don't like this, we right click and among the nesting choices we have add add search expression and such expressions are expression step are supposed to be executed in persistent storage, so that will be a database if your back and is connected to it, to one or it will be the xml file in our case, where we prototype against the xml file and if we are in turn key will be the persistence mapper that in turn will question the backing database alright, so let's just go ahead and add a search expression or maybe better yet, we will do a new view model to keep the searching and we will column this "person search" and we type it to be "person" right click and in the nested view models add search expression and what happened here, was that three columns were added to the root and one of the columns was a variable called the vSeek result, this variable was created and added to the viewmodel well it wasn't because it's implicit, but it should be in the newer versions, it will be and so variables are just as they sound something that we can define in the view model and is only available in the viewmodel scope, so this one should be of collection person this is where our result is going to end up from a search and that one we connect to a search result grid, so we have another variable vSeekParam that is defined as a string, so we have a column in the UI that lets the user enter a criteria and we have his search button and the search button as the ocl expression "selfvm.search", "selfvm" is a special instance that is available in view models only from OCL, let's see what it contains, "selfvm." and from here we can do things as refresh, save, search, and a few other things, like PSexpression_refresh, we can come back to these in later sessions, but for now we just going to use the vm search, what the search operator does is it looks for search expressions in the view model and this is a search expression, it's just another view model nesting, but what separates this from the other nestings is that it is not connected to anything it's judt sits here in the middle, doesn't need to be in the middle because I said so I can right click this and move this one up, so as such expression is typed and it has criterias right here it's just columns you can have many criteria per search expression the criterias are merged together with the ocl operator intersection, so what if these criteria is true and we had another or this criteria returned five persons 12345 and we had another one that return two persons 45, the intersection will take what's equal between the two domains so 4 and 5, but the search expression the criteria is just another ocl, but what's different about this is that is the persistent storage subset of SQL Ocl-PS it sets up here in the edge when we entry and then we don't have access to every single operator, we can't concatenate strings etc. in this language its main purpose is to be easily transformed to SQL and executed as an SQL query to the database and the database will return a number of identities, that we will in turn interpret as persons and load personal objects, so what we do is select and we have a loop variable called A then the mechanism to create the search expression and all this for us it just took the first string attribute of the class that we had set person and that was first name and set, well it's not unlikely that is what you as a developer want to limit search of, this attribute as SqlLike(vSeekParam) and ends with a +% just like in Sql operator like, so if you want to find both and start, if you want to find values that equals in the middle that you would go something like this, so this will be a resulting string that's add into the SqlLike, that of course will be translated into a like operator in sequel, but as we are running against an xml file, it will do something similar just execute operator on that so is this really what we want well, we want to also check if it's the last name maybe, so I use "or" and I use "LastName", like that what should I show for a result I can show the things I have first name and last name so let's do one thing more in this view and if you don't find what you expect you might want to have somewhere where you can create a new person, so let's totally action definitions for this dialogue and let's do a viewmodel action and say that we should show it on the root and say new person and the execute expression on this one should be PersonCreate, having done that we can see, if we have, we can save this push the play button, start system, Run Model and continue, we never created an action to actually show the seeker view model, so person search I right click on this and say add a global action for show okay then it's shown here, but we probably want to sort into as menu group a double click it find it here set menu group-seekers maybe, so this is might be where I want to put all my search dialogues and who knows having done that and I head back to this one model refresh, seekers, show per person, search and I can search, but I only want those that has an "a" in them that's the only one, okay but what if someone's missing I can create a new person and call that Andersson Anders, now if I search for a I should find Anderson, but since my xml file is, I guess it is case sensitive it is case sensitive, so if we don't like that we should have used operator called .sqlLikeCaseInSensitive, where like so now we have the searcher let's go back to the house view where we added the pic tenants action so the pick tenant action and let's do a copy of this, where did he go let's do a copy of this, just going to do a copy and paste, and "pick tenants by search" and that one should bring up the person search instead and if it does it cannot call "check this" because that variable doesn't exist in that UI like instead it calls "SearchResultGrid" if that is empty ok and this expression won't go either because the same problem, like that and it adds the tenants if I have selected any so if we head back here we see that we have another action pick tenants by search of course in the end, I only want one of these and our most likely it's the "BySearch" that will survive and then maybe I will change its name, model refresh, houses and pick one here, this doesn't have any tenants, I'm going to pick tenants by search, I'm going to search on find this one and I add that one, so I find it rather disturbing that I don't see the name here this is what I talked about before, in session 2 or something first, when we do the UI and watch the information together that it's obvious that, of course, we need to see the name here as a new requirement, but it's obvious now that we see the result and the not a problem this is the grid, which is this one, which points to this one and let's add the columns and add a generic column and in that generic column sets an expression that follow the role to tenant and the first name that's the ocl editor acting up when you don't have a separator first name and you might have noticed that I quite a lot of times had a need to concatenate first and the last name because that's simply how we refer to persons, so this sort of this pattern comes back again and again and we're going to solve this in just a minute, just going to save the fact that we did a new column and we call that "tenant name" and we might want to give that a little more space like three columns and we might want to drag this one to the end here and over there, and this one and we added in summary session it's just we want so if I save and refresh and look at all the houses, was it this one and there's Andersson, but I don't want it there I want it first and let's show the gridlines, like that, refresh like that and that's pretty obvious and how come this isn't even showing, well it's too tight to show with this style, so how would you solve that well as you can see we are cramming everything into one grid cell here so we're gonna insert column and give this one more space for the presentation let's give it 2 and just to make things look straight you're going to get the rest of them 2 as well, head back, refresh, views, all houses, when I click it would still crap but you get the general idea I will just insert yet another column let's judt do that one for and refresh, like that so this is important how quickly we can go from feedback with our eyes that this isn't good back to design how should be instead back to verification, okay it's fine it really saves everyboy's time ok enough about that, and I said that this pattern is repeated again and again yes it is the first name and last name it's a really common scenario that we want to refer to persons by their full name, so what we probably would want to do is add an attribute, that is called full name, but that wouldn't be very normalized to store the first name and the last name and full name, so let's make that one right, that's another attribute mode, it's not persistent as it is not stored in the database, it's derived as it's calculated from other values that we do have, so I can paste in that one and now that was for the tenants and I don't want that because now we are in the scope of a person, so first name and last name this makes up the full name and now we have done this and we can make use of it in our view models or wherever we access model information, so instead of doing this we can just as well do the full name, like that and now it's grey I was expecting it to be pink, because it is derived I wonder why that was it's derived don't have an answer, but going to save what do you say? self is not... that was just wrong, save and head back and model refresh, and there's really no difference, but like here now that we have it let's use it, so tenance last name and tenance full name is full name we got refresh if I were to change the name the right attributes were like this there are always subscribed, so let's head back to this view and add it as well just to prove a point all persons add column full name, give it some space when it's in grid too maybe we refresh, views, show all persons as soon as I change one of their values that build up the derivation, the derivation will kick in and invalidate as the UI looks at this value it will force it to refresh, getting the parts of the value and re-evaluate it, so when I write Hans it will be updated and if I were to change anything it will be updated and that might be Dick Smith, right, so derivation is also available for associations so what we could do, if we want to know where the person lives is of course to follow to see the rented apart and look up the street for that house but if that is a common operation that we want to do we could also add a association straight from person to streets and since I can rent many apartments, I potentially have many addresses, so if I want to derive this from available information, I was saying that the association is derived and I will take this end, will have no value so I will say that there it is non navigable, is navigable false, because if I would want to go from street to persons that would be another derivations that would have another expression, but this one should have a derivation expression, that it starts in person and it goes to here is the one that is derived it goes to owned house, no, to lease contract, and from lease contract rented apartments, and from rented apartments - the street I really must fix that, the street so this will be a collection of streets and if we were to show this in our UI, I guess we could add column and add generic column, and I follow the relation to streets and that has a name, but since this is a collection of strings, we need some way to display it in a single cell that we will do here in the grid and done an operator that's real handy for these cases as CommaList so it will take all the strings in the collection and append them as they with the comma in between, so lives at, so heading back to refresh, views or persons, so here we see the address is swelling ok, so good we have covered in a lot of ground we have mentioned derivations for attributes like the full night servations for associations like the street even if it was kind of silly, because we would probably would like the street number to get the precise address and that's not possible this way we have covered the idea of being able to vSeek in a lost database and then we also mentioned variables that are available in view models, so I'm going to show you another thing and what if we are in a situation where we actually need some test data, we need a lot of persons to verify that our idea to search in larger amount is valid and of course we could run the prototype print and press, we added the new person action here and we could press that a thousand times to enter the first and last name but is there a better way, you ask and since I talking about it you have probably guessed that there is and I go into the the Run button again because I need a context that we are in the XML persistence, we're going to start the system and we're going to go into the legacy debugger and in here we have a tab over here "import tab separated", so tab separated data import via named view model, so what it says he's given tab-separated data and the view model name assumes row 1 in data to be viewmodel column and creates instances of view model class so basically, if we have some data that we paste in here, we should be able to create objects of certain class, but it also says, that we need a view model, so let's create one, as you see the view models are used over and over for different purposes ImportPersons and type Person and let's assume the first name is the first value and the last name is the second value so that's about it and given that I should be able to say that this is the view model I want to use or maybe I need to reread this, I do start, lazy debugger, input tap separated and view model and get header from view model,and first-name lastname alright where can I get that, I found this site as google for a list of names and find anything on google list of random names let's do 50 and male and female and well no alliteration when you start the same ok now I want to grab these on listing text area, that's great, I wonder if this is tab separate it probably isn't and going to start notepad, alright so is that a tab no, I copy tab and I want to do is search and replace here, look for space and paste in my tab and replace it all and copy those and head back to my importer and paste those, and go, so that means I got a lot of dirty objects here that I will save like that and head back to my this one is going to restart, person search and I have some test data to work on oh let's see everyone that starts either their first loss name with "t" or has a "t" really because that was what we said in the criteria ok, so that means that when we do houses and we want to assign tenance by search and we do everyone with the "T" because it is case sensitive as we found out and select them and press ok then we have those as tenants alright moving ON as we see the tenants here, but they haven't got an apartment number...they haven't got a rent figure, but they really should this is important information it's so important, that we might want to add constraint on our class lease contract to make sure that the user of the system is made aware of the importance of these values so I select the class and I select constraints and I get a little dialogue where I can add constraints this constraint I give a name "must have apartment number" that's the name of my constraint so that I can refer to it and and I want to have a description as well and I'm going to make easy to myself is to do something like this, that's right the expression is more or less self.apartmentnumber and well it should be not null, right shouldn't be null and then now we got that symbol that says that this has one constraint, so when we look at our diagrams we will see that this is constrained in some way ok, so if we were to head back to our prototyper and show the house we see, must have apartment number must have apartment number, but there's really no information on who is missing the apartment number and let's head back to the constraint and in the description we can actually access attributes, so and we can go like this as string within the larger than and smaller than, greater than and tags to say that we want to describe the default presentation here, can you please inject that and what is the default presentation, default string representation on lease contract is none okay, but we might follow the link to the person and use the full name again we made use of the derived full name like that and save, and head back, refresh, view all houses, so Hans Karlsen must have an apartment number and Dick Smith must have apartment number and as I give our Hans Karlsen apartment number one that is removed and as I give Dick's one 2 that one removed as well, so that's a good way to feedback information to the user about what needs to be filled in but it might not be enough for us, we might need to stress these even harder depending on use case so there's more ways to signal the user that something needs to be done if we check the house view here and we had the variables that we don't use in this view we use them in the seeker, but we also have the the constraints, so these are the constraints that we found in the classes that are used here that is just one and depending on use case we might not want to show it because who knows the view might not even contain their apartment number, so no need to stress the user about entering it if it isn't really possible, so that we could just opt it out, but we want to have it opt-in because it's good for us, but what we could do is something more precise as a validation rule let's right-click up in the top and add a validation rule, so we got rule one and then the rule one is that let's say it's the fact that the selected, what what I want to do is to highlight something here apartment number to make the user see this so what is this, this is here the lease contract, so what I want to do in my validation rule is to find a variable the current the lease contract and check that one that particular one that sunscreen and or selected at the moment, and check that for apartment number and verify that isn't null, and then I can write something please supply number like that, but we still haven't been able to say that this rule is supposed to show up for this field that I can select the field it's over here and I'm supposed to find it and validation rules, my menus really turn out the wrong end all the time, validation rules, rule one, please supply number ok, so that would be one way to further gearsteer our user to see something, but how does it look refresh, view, houses it doesn't show anything, but if I null that out first I get this one and I also get the red information here actually depending on what style you use it really renders differently, so that you can control this and we have examples, where you just have an "!" that was when you point that it states what's wrong with it so this is another important thing I should mention that,when you have errors and there's some something and updated in the information and you try to save then it will ask you, there are errors in the information, do you really want to save anyway? "Hans Karlsen must have apartment number" and the system won't stop you from saving and this is an important principle I think, that you shouldn't stop the user from entering information, even if it isn't correct then it's better to to monitor all the information that is in incorrect, so that they can come back to it then and update it don't stop users from entering data and make a UI very clear, what you expect but you should always always honor the users' request to save and maybe you should work with the quality attributes like states that you can't go into approved, before you have apartment number or the rent in dollars, but you shouldn't stop them from saving ok, that's just my very clear view on this ok, so I'm going to save it anyway, but run nice wouldn't you say just having the area information this way, so whenever I enter something the error goes away and of course I don't get the warning, when I save, but that was not a very good side for this example, so switch back, so let's add another constraint and we make that not to error constraint, but rather look at the other types of constraints, so we have a constraint the "rent" and the description and we do as we before "<as string> lives free" and we don't do an error just the information expression would be self.rent->not null because when the expression is true then the constraint is fulfilled and we don't shoe anything, but as soon as the constraint is not true then it's broken and then we show warning signs etc. in this case information refresh and now it's a little white thing is Hans Karlsen lives free shouldn't be the case that let them say alright I wonder if we will have time to cramming reports in this, so that we could do rents and rents slips for these guys I think maybe we'll come back to that in the next session so we will round this off and thank you very much for following along with these tutorials and I'll be back
| | [[Category:Derivations]] |
