问题
I have a Class and I need to get genre object, put in an array, get unique value (because I will have many) and use the array to populate section of a tableView.
I have the following code:
class Movie {
var name: String!
var plot: String!
var imageUrl: String!
var genre: String!
init(name: String, plot: String, img: String, genre: String) {
self.name = name
self.plot = plot
self.imageUrl = img
self.genre = genre
}
}
}
import UIKit
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
@IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
tableView.delegate = self
tableView.dataSource = self
}
var loadMovie = [Movie]()
let insertMovie = Movie(name: "Blow", plot: "Blow bla bla bla", img: "", genre: "Action")
let insertMovie2 = Movie(name: "BLade", plot: "Blade bla bla bla", img: "", genre: "Action")
let insertMovie3 = Movie(name: "Inside Out", plot: "Blow bla bla bla", img: "", genre: "Kids")
let insertMovie4 = Movie(name: "Titanic", plot: "Blow bla bla bla", img: "", genre: "Drama")
loadMovie.append(insertMovie)
loadMovie.append(insertMovie2)
loadMovie.append(insertMovie3)
loadMovie.append(insertMovie4)
let unique = NSSet(array: loadMovie.map { $0.genre })
unique returns the unique value ( Action, Drama, Kids), but when I try to get section:
func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return unique[section].genre
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return unique.count
}
it doesn't work.
Where am I wrong?
回答1:
Filtering the movies by genre each time the table view is reloaded is quite expensive.
This is a solution using an array of header (genre) names and a dictionary containing a [Movie] array for each genre respectively.
var unique = [String]()
var loadMovie = [String:[Movie]]()
Add a method to insert the movies. The logic is:
• If the genre exists, add the movie for that genre to the [Movie] array in the dictionary.
• If the genre does not exist, add the genre to the unique array and the movie to the dictionary.
func insertMovie(movie : Movie) {
let genre = movie.genre
if unique.contains(genre) {
loadMovie[genre]!.append(movie)
} else {
unique.append(genre)
loadMovie[genre] = [movie]
}
}
Now insert the movies
let movie = Movie(name: "Blow", plot: "Blow bla bla bla", img: "", genre: "Action")
insertMovie(movie)
let movie2 = Movie(name: "BLade", plot: "Blade bla bla bla", img: "", genre: "Action")
insertMovie(movie2)
let movie3 = Movie(name: "Inside Out", plot: "Blow bla bla bla", img: "", genre: "Kids")
insertMovie(movie3)
let movie4 = Movie(name: "Titanic", plot: "Blow bla bla bla", img: "", genre: "Drama")
insertMovie(movie4)
The relevant data source and delegate methods are
override func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return unique[section]
}
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return unique.count
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let genre = unique[section]
return loadMovie[genre]!.count
}
In cellForRowAtIndexPath populate the cells with
...
let genre = unique[indexPath.section]
let movie = loadMovie[genre]![indexPath.row]
cell.textLabel!.text = movie.name
...
An alternative is an array of arrays
回答2:
An update for Swift 4
func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return unique[section]
}
func numberOfSections(in tableView: UITableView) -> Int {
return unique.count
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let genre = unique[section]
return loadMovie[genre]!.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "basicCell", for: indexPath)
let genre = unique[indexPath.section]
let movie = loadMovie[genre]![indexPath.row]
cell.textLabel!.text = movie.name
return cell
}
来源：https://stackoverflow.com/questions/35457371/unique-value-of-object-to-use-in-section