Day 13

Thread 2, Day 13 - Friday, February 3, 2023

Agenda

Finding Square Roots
- You can review the history of commits for this project to understand the simplest possible flow for handling user input that is expected to be numeric.
- We must take a String, convert it to an optional Double, then unwrap the optional to a regular Double so we can do arithmetic with the value, and finally, produce String output again:
```
flowchart LR

id1["Step 1\nString"] --> id2["Step 2\nDouble?"]
id2 --> id3["Step 3\nDouble"]
id3 --> id4["Step 4\nString"]
```
Share the Bill: Opportunities for Further Abstraction
- A complete example that ties together all concepts we have learned so far in this module
  - Optionally, you can review how it was built, step by step
  - In the list of commits, click the commit details badge to see what changed within that specific commit:
- Please fork and clone the repository for this app now
  - With a partner, review the code within the body property
    - What opportunities for eliminating repetitive code do you see?
    - Let's improve this now...
    Note
    
    Here is the video from this discussion in class – how to apply abstraction.
Share the Bill: Add a Second Tab to Show History
- Data to be saved within an app should be created in one location only
  - Put another way, a given piece of data must have just one single source of truth
  - Currently this occurs with the @State property wrapper
  - How, though, can we share data between screens?
  - That is where the @Binding property wrapper is useful
    - In brief:
```
flowchart TD

id1["App Entry Point\n@State"] --> id2["Screen 1\n@Binding"]
id1 --> id3["Screen 2\n@Binding"]
```
    - Let's examine this together now...
    Note
    
    Here is the video from this discussion in class – how to share data between screens using @Binding
End-of-module Task: Make an Interactive App

To-do items

Before our next class...

Begin working on your end-of-module task.