Training:The 1000 steps program to MDriven Chapter 7

This is chapter 7 of the training material - if you want to start from the top: The_1000_steps_program_to_MDriven, chapter 6 is found here

Here is the video for Chapter 7: https://youtu.be/QxXA5D4mEio

Video 7 : MDrivenEducationVideo step 215-238 :

Title	Content	Time(segment start)
Introduction	Introduction	00:00
Renaming and notes	Renaming and notes.	00:08
Derived	AttributeMode: derived Ordering a list in OCL	04:00
Tagged value	Adding tagged value, making value editable	15:55
DateTime	Type DateTime, IsStatic	22:25
Selectbox	SelectBox(singlelink with setter)	30:03

And here are the steps as text:

Chapter 7, First mention of Derived Attributes, Editable Grid cells in Web UI

215 CarsIUsedToOwn is actually a poor name - if we change the name to CarsPersonUsedToOwn its a better fit as it does not raise questions about whom "I" refers to. Type the new name in the Association end - save (that will run the error check) - see the many errors

216 Change it back to CarsIUsedToOwn temporarily, save , no errors

217 Instead of changing it we will use the Rename-function that will help to rename everywhere it is used. Right click the association end - choose rename, new name: CarsPersonUsedToOwn - Check "Set former name" - and whenever you use "Rename" you should check "Set former name" to help MDriven to help you once your changes also involves creation of change scripts to a database.

Save - verify error free.

218 Create a Note on the diagram by right clicking "Add note" - double click the note box - write this in the note: We will assume that a person always has 1 car at a time - and that person immediately gets a new car on the same day the person sells the first.

Close the Note - resize and place it somewhere nice

219 Add a new attribute DatePurchased of type DateTime? in class HistoricOwnership

220 Select DatePurchased and In the property inspector - change the AttributeMode from Persistent(default - means saved in the database) to Derived (means calculated somehow)

221 Stay in the property inspector - find DerivationOcl - click up ocl editor with the three dots

222

we want THIS DatePurchased to be derived from the prior cars DateSold

we want to have an expression that from HistoricOwnership (self) goes up to the person (self.Person) and from there looks at all HistoricOwnership (self.Person.HistoricOwnership), makes sure that this list is in DateSold order (self.Person.HistoricOwnership->orderby(h|h.DateSold) ), and check where in this list THIS HistoricOwnership (self) is (self.Person.HistoricOwnership->orderby(h|h.DateSold)->indexof0(self) ) and once we have that grab the one after THIS HistoricOwnership : listinorder->at0(listinorder->indexof0(self)+1)

We find that we need the same list twice and its seems fair to get it once and then use it in the expression twice. This is done in ocl with the "let x=someexpr in someotherexpr" operator.

We can write:

let  listinorder=self.Person.HistoricOwnership->orderby(h|h.DateSold) in

(

listinorder->at0(listinorder->indexof0(self)+1)

)

This expression will return a HistoricOwnership object - but we want THIS DatePurchased to be derived from the prior cars DateSold - so we append .DateSold

let  listinorder=self.Person.HistoricOwnership->orderby(h|h.DateSold) in

(

listinorder->at0(listinorder->indexof0(self)+1)

).DateSold

223 Go to Person viewmodel - add the date purchased in the HistoricOwnershipGrid - save - test web

224 We notice that there is no good way for us to edit the DateSold - and thus the DatePurchased will get null all the time. Make the grid Editable by selecting the HistoricOwnership nesting head (blue)

225 Here we will add a tagged value - tagged values are extra meta information we can dress up our model with on most levels, like classes, attrtibutes and viewmodels. Press the Tagged values button in the ViewModelEditor.

226 In the shown window - press the Refresh from wiki button. Note how many predefined possible values (value store) are shown. You are not limitited to these tagged values - but the predefined has special meaning to Turnkey (the web front end engine, or to Wecpof the WPF engine)

227 Find Editable in the top selector Add that - set its value to True - close save

228 In order to make a cell in a grid editable it must be in an editable grid - and we fixed that just now - but a column must also have an ReadOnly expression that does NOT result in true (but rather false or left empty) - clear the DateSold viewModelColumn in the grid ReadOnlyExpression

229 Save - test web - you have an editable datepicker in date sold

230 Enter some different dates in the rows - if you dont have rows - add some - notice the instant calculation of the DatePurchase as the DateSold comes available on the row after

231 Click the DateSold column head in the grid  - to verify you get the correct values

232 in the column DatePurchased we want to force iso date - and not trust browser setting to change expression to self.DatePurchased.ToString('yyyy-MM-dd'). Save test web

233 Discover the issue with use taking IndexOf0 +1 one - when the prior car is at -1 - fix derivation. Save test web

234 Notice the Name column - it now looks like an edit box - this is because we made the grid editable. Set column to IsStatic=true - save , verify in now looks like simple string

235 We actually dont even want the Name column here - since it will always be our own name - drop it

236 From class Car drag out new association arrow to Person - The Car-end you name CurrentCar and the Person-End you name CurrentOwner

237 In the Person ViewModel - add a SelectBox by right clicking in the green tree,Add Nesting ViewModelClass, SingleLinkWithSetter, CurrentCar - save, test web

238 Clean up the view and remove bogus columns

Next: The_1000_steps_program_to_MDriven_Chapter_8