Run a function that is stored in an array - Swift - arrays

Question

I have recently started coding for iOS and using Swift. I am trying to build a small quiz app for practice. However, I am having an issue running a function that is stored in an array.
My question library swift file is as follows:
func getQuestionLibrary() -> NSArray {
var questionLibrary = [
[
"categoryName": "General Knowledge",
"functionName": generalknowledgeLibrary()
]]
As you can see it states the category and stores a function.
My code that works fine, uses this array (there are more entries) to dynamically create a list of categories to choose from. When a category is run it performs a segue and moves onto a view to display the categories.
If I hard code in the categories that app works great:
if playQuestionLibraryText == "General Knowledge" {
questionPack = generalknowledgeLibrary()
} else if playQuestionLibraryText == "Music" {
questionPack = musicLibrary()
} else if playQuestionLibraryText == "Film" {
questionPack = filmLibrary()
}
However, as the list is dynamic I would prefer it not to be hard coded.
Please can you assist me to allow the my code to search the array and run the function stored as functionName in the array when the correct category has been selected.
Thank you in advance.

Answer 1

The code:
"functionName": generalknowledgeLibrary()
Sets "functionName" to the result of calling the function.
Use:
"functionName": generalknowledgeLibrary

Answer 2

You are looking up a 'library' based on its name; use a Dictionary. Your 'library' is going to hold some stuff (as libraries are wont to do) and allow some behaviors - so capture it as an abstraction.
class Library { // maybe this is a 'questionPack'
// stuff in a library // that is okay, change the name
}
var libraryMap : [String:Library] =
["Music": Library(/*...*/),
"Film" : Library(/*...*/),
"General Knowledge" : Library(/*...*/)
// ....
]
if let library = libraryMap[playQuestionLibraryText] {
// do something with the library
}

Answer 3

i did a code to this question, using subscript
I created a class collection to manage your question. I believe the friend solution just remove () is more easy and correctly, but i created this class to complement my studies, because this I like enter here to try new solutions.
class QuestionCollection
{
struct QuestionItem {
var categoryName:String;
var function:()->Void //Here can add return type you need
}
private var dicCallbacks:[String:QuestionItem] = [String:QuestionItem]();
func add(categoryName:String, closure:()->Void //Here can add return type you need )
{
dicCallbacks[categoryName] = QuestionItem(categoryName: categoryName, function: closure);
}
subscript(categoryName:String)->()->Void //Here can add return type you need
{
get
{
if let callback = self.dicCallbacks[categoryName]
{
return callback.function;
}
return error;
}
set
{
dicCallbacks[categoryName] = QuestionItem(categoryName: categoryName, function: newValue);
}
}
func error()->Void
{
println("error try catch closure function")
}
}
How use this class
func musicTest()
{
println("test Music");
}
func musicGK()
{
println("test Music");
}
func musicFilm()
{
println("test Music");
}
var questionCollection = QuestionCollection();
questionCollection["Music"] = musicTest
questionCollection["General Knowledge"] = musicGK
questionCollection["Film"] = musicFilm
questionCollection["Music"]();
questionCollection["General Knowledge"]();
questionCollection["Film"]();

Answer 4

Sorry for slow reply. I changed my code as this works instead and I am happy with how it works.
The questions in the future will be populated via the internet via a loop.
struct Question {
var categoryName : String
var questionTitle : String
var answerA : String
var answerB : String
var answerC : String
var answerD : String
var correct : String
}
public struct QuestionLibrary {
var questions: [Question]
}
let QuizQuestions =
QuestionLibrary(
questions: [
Question(
categoryName: "General Knowledge",
questionTitle: "Question 1",
answerA: "A", answerB: "B", answerC: "C", answerD: "D", correct: "D"),
Question(
categoryName: "Music",
questionTitle: "Question 2",
answerA: "A", answerB: "B", answerC: "C", answerD: "D", correct: "A"),
Question(
categoryName: "Film",
questionTitle: "Question 3",
answerA: "A", answerB: "B", answerC: "C", answerD: "D", correct: "B")
])
My code then to retrieve questions based on the category is:
let questionLibrary = QuizQuestions.questions
var questionPack: Array<Question>?
questionPack = questionLibrary.filter({c in c.categoryName == "Music" })
I then select a random question
let question = questionPack![randomNumber]
And to display the question text is
question.questionTitle
So, my earlier question was about running functions in an array which I learnt I didn't need to do. But least I've answered so it might have others who need similar code :)