View: View displays the information that is contained in the Model. The UIkit framework contains classes to draw typical interface elements such as tables (lists), buttons, textfields, sliders, and so on.

Remember, View and Model do not communicate directly, they work via Controller. The following is the UI part of application that is nothing but View of application:

Model: Model contains the data. The Model objects obtain the data either from a database or the files that could be located locally or externally. The data can be obtained from hardcoded values or web services. Model also represents the logic that manipulates and processes the data, as follows:

NSString *password =
[NSStringstringWithFormat:@"secret_password"];

Here secret_password is hardcoded value that is nothing but Model.

Controller: It acts as a mediator between Model and View. Now, here Enter Password is an action. So, whenever the user enters the password from View and hits enter, the request goes to Controller that checks the data in Model and if the password does not match, it informs the Controller and then Controller notifies it to View. Controller asks Model to validate the user password and once it gets the response from Model, it will notify the View whether the user has entered the correct password or not. Hence, View shows the Incorrect Password message, as shown in the following screenshot:

Now, if the data entered in View matches with the data in Model, then the message will be displayed as follows: