Fox Valley Girls Coding Club

Coding Tonight!

Tonight’s meeting will focus on continuing the development of the WeatherWear Web Service and the Swift app to consume the Web Service.

Notes on Swift String Interpolation Issue with Optional variables:

String Interpolation in Swift: the term “string interpolation” refers to creating a character string that pulls values out of one or more variables and combines those values with other characters to form a string. The entire expression is enclosed in double quotes and each variable within the string is preceded by a backslash and enclosed in parentheses. Example “Hello \(name)”  will print “Hello Gandalf” if Gandalf is the value in the variable name.

Optional Variables in Swift: Swift is strongly typed and insists that if there is a possibility that a variable (or constant) may not have a value at some point when the program is running, then it must be declared as optional. The variable may then  either contain a value of the declared type or may be nil.  The purpose is to avoid the null reference errors that can occur in other languages when someone tries to use a variable without a value. Declare a variable as optional by putting a question mark at the end of the type such as our WeatherForecast:

var forecast: WeatherForecast?

When using the values in an optional variable, the variable needs to be “unwrapped”, like removing it from a box. Consider a cardboard box labelled “Weather Forecast”; you can open it up to find a forecast object or you can find nothing, so you can’t treat it as if there is always a value there.  There are several ways to unwrap and to check what is in the box, but for this problem we will force unwrapping explicitly.

The Problem with String Interpolation with Optionals:

When we tried to display the temperature in either Fahrenheit or Celsius by drilling down through the many nested levels of objects in our WeatherForecast we were getting this warning and the text on screen was gibberish:

The fix is to explicitly unwrap the values at each object level by putting an exclamation point in place of the question mark in multiple places, i.e., after each object name within the long nested object:

Jellyvision Field Trip Debriefing

Last Friday, on a day off from school,  9 of our members enjoyed an amazing day at Jellyvision, getting an inside look at what it is like to work at this tech company in a very wide variety of different roles, technical, business, and creative. Many of the brilliant and talented people at Jellyvision gave their time to make this a very special event for all of us.  Kate from Jellyvision will be attending our meeting this Friday and we will have an open discussion about the experience and insights gained. How were you inspired?  What did you learn?

Continue Developing Web Service and Client

We will work in our Web Service and Swift teams to continue developing the Weather Wear Service and the Swift client app to send a request to the service and display results.

Some notes on what we have so far in our Swift Client:

Consuming a Web Service in Swift

We will meet at our usual time and place: 5:45 PM at 25N Coworking

Finalize Plans for our Jellyvision Field trip!

Continue working on our multi-component Weather Wear software :

• Review overall solution architecture: 

  • Lucid Chart diagram by Robin

• C#/Swift Tutorial: Learn/review some object-oriented concepts

  • Classes and Objects: Properties (values) and Methods (behaviors defined in functions/procedures)
  • How are they defined and used in C#? In Swift?
  • Objects as Models for Data:
    • Tools:
      • Online tool to convert JSON to CSharp
      • Online JSON Viewer showing object structure
    • What is the data model for the JSON returned from the Weather Underground API Request for the Forecast?
    • What is the data model for the JSON returned from the API of the WeatherWear Web Service we are building?
    • Can/should the WeatherWear data model inherit the Weather Underground Forecast data model?

• Web Service Team:

  • Merge Web API code with the GitHub Repo
  • Continue work on algorithm and implementation of the WeatherWear Web Service and the console app to test it

• Swift Team:

  • MVC: Model/View/Controller design pattern
    • Model represents the data model defined in a class; we will create a model class for the Weather Forecast, and later for the WeatherWear API Response
    • View is the Presentation Layer, i.e, the screen the user sees
    • Controller: Code that handles the user input, talks to the model, handles interactions between Model and View. In Swift, we will define a Class for the controller; there will be a ViewController Class defined for each View
  • Review/Learn how to connect UI elements to code. Elements in the UI designed on the storyboard need to be connected to code in the appropriate controller:
    • @IBOutlet: in a code module, an Interface Builder Outlet is a variable that holds a reference to an element on the storyboard. Example:  our screen has a label to display a city name and we need our code to be able to access it. We add this to our view controller:

 @IBOutlet weak var cityLabel: UITextField!

• • •  @IBAction: in a code module, an Interface Builder Action is a function that is connected to a user interaction with a UI element. Example: update the city label when the user clicks a button. We add a connection between the function named GetWeather and the button; then define the action inside the function

      @IBAction func GetWeather(_ sender: Any) { cityLabel.text = “Geneva”    }

  • Start setting up the code to send the Web API Request for WeatherWear
    • We will initially set up code to access the existing Weather Underground Forecast API