Designing cross-platform GUI apps with Fyne
Storing Data
You now have a fully functional app to track your to-do items, but the app will forget the items when you exit. To remedy this, you can connect to a database or store data in a file. However, Fyne lets you store your data in Preferences, a simple key-value store used to easily keep track of user interface state and small data storage without worrying about file storage or connection handling. You can access this feature using the Preferences() method on the App type created earlier.
Loading To-Do Items
You need to ensure that any existing to-do items are loaded when the app starts. To do this, you can simply set up the todos variable to be the result of a load call. Immediately before calling loadUI, you need to call
list = loadTODOs(a.Preferences())
This call will pass your application preferences to a new loadTODOs function that will return a slice of all stored to-dos.
Saving the Data
Before you have data to parse, you need to save it! To do this, you will use another new method, saveTODOs, which will take the current slice to save and a reference to the preferences you will be using:
saveTODOs(todos, p)
Be sure to call this method inside deleteTODO and addTODO after updating the data.
The methods that actually do the work in this example are really simple – you just concatenate all the items to a single string using a joiner constant and then split the items out on load, as shown in Listing 11.
Listing 11
storage.go
01 package main
02
03 import "fyne.io/fyne/v2"
04
05 const joiner = "|"
06
07 func loadTODOs(p fyne.Preferences) []string {
08 all := p.String("items")
09 if all == "" {
10 return []string{}
11 }
12 return strings.Split(all, joiner)
13 }
14
15 func saveTODOs(items []string, p fyne.Preferences) {
16 allItems := strings.Join(items, joiner)
17 p.SetString("items", allItems)
18 }
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