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Question Do I really need to pass data from view to model each time I edit the GUI data and want to compute something ? Then pass the new data back from model to view ? Is that how it should be done ?

I understand this is fine for a small GUI that does heavy computation in the model. But what about a big GUI, like a big table or a spreadsheet.

Question Do I really need to pass data from view to model each time I edit the GUI data and want to compute something ? Then pass the new data back from model to view ? Is that how it should be done ? I understand this is fine for a small GUI that does heavy computation in the model. But what about a big GUI, like a big table or a spreadsheet.

Answer Here are the elements that I took from the discussion with @dcorking: You have to update the data yourself. One shortcut is to update on a per-case basis, only what needs to be updated and don't touch the rest. Obviously, if you are sorting the collection after a single change, you may need to re-update the whole GUI eitherway. "Observers" have been mentionned that sounds like an automated way to do as above.

#The model package

class Collection():
    def __init__(self, name=""):
        self.name = name
        self.items = []

    def sort(self):
        self.items.sort(key=lambda x:float(x.price))m(name,price))

class Item():
    def __init__(self, name="", price=0.):
        self.name = name
        self.price = price

class Gui():
    #The View part.
    def __init__(self):
        self.collection = model.Collection()
        ...then fill the View with widgets (Menus, EditTexts, Buttons, ...)
        
    #The Controller part starts here
    def setViewFromModel(self):
        self.someEditText.setText(self.collection.items[0].name)

    def setModelFromView(self):
        self.container.items[0].name = self.someEditText.getText()
    
    def onClickSort(self):
        self.setModelFromView()#Read the GUI data
        self.collection.sort()#Compute in Model
        self.setViewFromModel()#Update the View with new data
        

#The model package

class Collection():
    def __init__(self, name=""):
        self.name = name
        self.items = []
        self.itmesToUpdate = []

    def sort(self):
        self.items.sort(key=lambda x:float(x.price))
        self.itemsToUpdate = []
        self.itemsToUpdate = listItemsThatWereMovedAround()

class Item():
    def __init__(self, name="", price=0.):
        self.name = name
        self.price = price

class Gui():
    #The View part.
    def __init__(self):
        self.collection = model.Collection()
        ...then fill the View with widgets (Menus, EditTexts, Buttons, ...)
        
    #The Controller part starts here
    def setViewFromModel(self):
        for i in self.collection.itemsToUpdate:
            self.editTextName[i].setText(self.container.items[i].name)
            self.editTextPrice[i].setText(self.container.items[i].price)
        self.collection.itemsToUpdate = []# reset the list

    def setModelFromView(self):
        for i in self.collection.itemsToUpdate:
            self.container.items[i].name = self.editTextName[i].getText()
            self.container.items[i].price = self.editTextPrice[i].getText()
    
    #CALLBACKS
    def onItemModified(self, index):
        self.collection.itemsToUpdate.append(index)

    def onClickSort(self):
        self.setModelFromView()#Read the GUI data
        self.collection.sort()#Compute in Model
        self.setViewFromModel()#Update the View with new data
        

I have a question about MVC pattern, concerning the controller part.

Most of the program I happen to write are basically spreadsheet like. They are written in C/GTK+ and Python3/Qt5/Tkinter but share a common design : I separate the gui from the logic (data struct and heavy lifting methods) that seems to be the MVC pattern.

Question Do I really need to pass data from view to model each time I edit the GUI data and want to compute something ? Then pass the new data back from model to view ? Is that how it should be done ?

I understand this is fine for a small GUI that does heavy computation in the model. But what about a big GUI, like a big table or a spreadsheet.

Pseudo/Python Code

Let's consider a basic collection of items (shopping list, book library, ...). My main class Collection contains a list (dozens or hundreds) of Item and methods to be applied on the list.

#The model package

class Collection():
    def __init__(self, name=""):
        self.name = name
        self.items = []

    def sort(self):
        self.items.sort(key=lambda x:float(x.price))m(name,price))

class Item():
    def __init__(self, name="", price=0.):
        self.name = name
        self.price = price

Now the Gui part:

class Gui():
    def __init__(self):
        self.collection = model.Collection()
        #Build the gui
    
    def onClickSort(self):
        self.setModelFromView()#Read the GUI data
        self.collection.sort()#Compute in Model
        self.setViewFromModel()#Update the View with new data
        

Is this design fine ? For spreadsheet-like app ? Thank you.

I have a question about MVC pattern, concerning the controller part.

Most of the program I happen to write are basically spreadsheet like. They are written in C/GTK+ and Python3/Qt5/Tkinter but share a common design : I separate the gui from the logic (data struct and heavy lifting methods) that seems to be the MVC pattern.

Question Do I really need to pass data from view to model each time I edit the GUI data and want to compute something ? Then pass the new data back from model to view ? Is that how it should be done ?

I understand this is fine for a small GUI that does heavy computation in the model. But what about a big GUI, like a big table or a spreadsheet.

Pseudo/Python Code

Let's consider a basic collection of items (shopping list, book library, ...). My main class Collection contains a list (dozens or hundreds) of Item and methods to be applied on the list.

#The model package

class Collection():
    def __init__(self, name=""):
        self.name = name
        self.items = []

    def sort(self):
        self.items.sort(key=lambda x:float(x.price))m(name,price))

class Item():
    def __init__(self, name="", price=0.):
        self.name = name
        self.price = price

Now the Gui part:

class Gui():
    #The View part.
    def __init__(self):
        self.collection = model.Collection()
        ...then fill the View with widgets (Menus, EditTexts, Buttons, ...)
        
    #The Controller part starts here
    def setViewFromModel(self):
        self.someEditText.setText(self.collection.items[0].name)

    def setModelFromView(self):
        self.container.items[0].name = self.someEditText.getText()
    
    def onClickSort(self):
        self.setModelFromView()#Read the GUI data
        self.collection.sort()#Compute in Model
        self.setViewFromModel()#Update the View with new data
        

Is this design fine ? For spreadsheet-like app ? Thank you.