Back in the old Objective-C days I would often use enums for things like tables with constant contents, segmented controls, etc - in situations where there was an enforced incremented list of integers starting at zero. I would also often add a ...count member at the end to give a count of the entries, useful for table section & rows. Trying to do this with swift enums is proving troublesome - lots of conversions to & from raw values and extra default clauses in switches to allow for the 'count' entry. Can anyone suggest a graceful method of dealing with these sorts of situations?
Automatic increment is still available in Swift.
enum Section: Int {
case A = 0
case B
case C
}
Section.C.rawValue // -> 2
As for count, you should implement it manually (as How do I get the count of a Swift enum?):
enum Section: Int {
case A = 0
case B
case C
static let count = C.rawValue + 1
}
As for "conversions to & from raw values and extra default clauses" problem, compare with enum instead of its rawValue.
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return Section.count
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch Section(rawValue: section)! {
case .A: return 1
case .B: return 2
case .C: return 5
}
}
If you want to do something like array[Section.A], you can easily implement it.
extension Array {
subscript(section: Section) -> T {
return self[section.rawValue]
}
}
extension NSIndexPath {
convenience init(forRow row: Int, inSection section: Section) {
self.init(forRow: row, inSection: section.rawValue)
}
}
let array = ["foo", "bar", "baz"]
array[.B] // -> "bar"
let indexPath = NSIndexPath(forRow: 20, inSection: .C)
indexPath.section // -> 2
indexPath.row // -> 20
And so on.. :)
Add a function "count" to each enum. For example
static func count() -> Int { return 3 }
Integer -> enum conversion is done by the init method.
Related
My UITableView has two sections, so I created an enum for them:
private enum TableSections {
HorizontalSection,
VerticalSection
}
How do I switch with the "section" var passed in numberOfRowsInSection delegate method? It seems that I need to cast "section" to my enum type? Or is there a better way to accomplish this?
The error is "Enum case "HorizontalSection" not found in type 'int'.
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case .HorizontalSection:
return firstArray.count
case .VerticalSection:
return secondArray.count
default
return 0
}
}
In order to do this, you need to give your enum a type (Int in this case):
private enum TableSection: Int {
horizontalSection,
verticalSection
}
This makes it so that 'horizontalSection' will be assigned the value 0 and 'verticalSection' will be assigned the value 1.
Now in your numberOfRowsInSection method you need to use .rawValue on the enum properties in order to access their integer values:
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case TableSection.horizontalSection.rawValue:
return firstArray.count
case TableSection.verticalSection.rawValue:
return secondArray.count
default:
return 0
}
}
Jeff Lewis did it right, to elaborate on that and give the code litlle bit of more readiness -> my way of handling these things is to:
Instantiate enum with the raw value -> section index
guard let sectionType = TableSections(rawValue: section) else {
return 0
}
Use switch with section type
switch sectionType {
case .horizontalSection:
return firstArray.count
case .verticalSection:
return secondArray.count
}
Ok, I figured it out, thanks #tktsubota for pointing me in the right direction. I'm pretty new to Swift. I looked into .rawValue and made some changes:
private enum TableSections: Int {
case HorizontalSection = 0
case VerticalSection = 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case TableSections.HorizontalSection.rawValue:
return firstArray.count
case TableSections.VerticalSection.rawValue:
return secondArray.count
default
return 0
}
}
Currently I'm populating my UITableView by:
var eventDates: [NSMutableDictionary] = []
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return eventDates.count
}
Every eventDate within eventDates has a valueForKey("monthsYear").
Hardcoded I want now eventDates.count only return the eventDates with the valueForKey("monthsYear") == "September 2016".
In other words, to explain it one more time:
eventDates.count = 10. But only 5 of them match the condition valueForKey("monthsYear") == "September 2016".
How do I get only those 5 elements to populate the UITableView (with only 5 rows).
In theory something like this:
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let returnValue = 0
for date in eventDates where date.valueForKey("monthsYear") == "September 2016" {
returnValue++
}
return returnValue
}
Help is very appreciated.
So what you need to do is a simple Filter
let sepDates = eventDates.filter() { $0.valueForKey("monthYear") == "September 2016" }
return sepDates.count
some not answer related stuff stuff
One Advice, try to use models to avoid using valueForKey, so you array would look like
var eventDates: [EventDate] = []
good luck and have fun ;)
I have a UITableView with sectionIndexTitles. Here's my data source :
let sSectionTitles = ["A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","#"]
var sectionTitles = [String]()
func sectionIndexTitlesForTableView(tableView: UITableView) -> [String]? {
return sSectionTitles
}
func tableView(tableView: UITableView, sectionForSectionIndexTitle title: String, atIndex index: Int) -> Int {
var section = 0
if let selectedSection = sectionTitles.indexOf(title) {
section = selectedSection
} else {
section = index
}
return section
}
The variable sectionTitles is a similar array to sSectionTitles except that it only contains section indexes that are valid. For example, if I have no Contact with their name starting with the letter D, then "D" won't be in sectionTitles.
I'm trying to replicate the behavior in the Contact application :
If the user clicks on the Index title "D" and if there is at least one contact in the B section, then scroll to this section.
Else, scroll to the previous section available. (In this example, if there are no contacts for the B and C letter then scroll to A)
I've been stuck of this for many hours I still don't know how I could apply this logic. I thought about using a recursive function but I didn't manage to pull this off. Does someone has any lead on how this could be achieved?
Thanks.
I think you can do it by recursion. Use another helper function to retrieve the appropriate index and call it from tableview data source function. Example,
func tableView(tableView: UITableView, sectionForSectionIndexTitle title: String, atIndex index: Int) -> Int {
var section = getSectionIndex(title)
return section
}
//recursive function to get section index
func getSectionIndex(title: String) -> Int {
let tmpIndex = sectionTitles.indexOf(title)
let mainIndex = sSectionTitles.indexOf(title)
if mainIndex == 0 {
return 0
}
if tmpIndex == nil {
let newTitle = sSectionTitles[mainIndex!-1]
return getSectionIndex(newTitle)
}
return tmpIndex!
}
My UITableView has two sections, so I created an enum for them:
private enum TableSections {
HorizontalSection,
VerticalSection
}
How do I switch with the "section" var passed in numberOfRowsInSection delegate method? It seems that I need to cast "section" to my enum type? Or is there a better way to accomplish this?
The error is "Enum case "HorizontalSection" not found in type 'int'.
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case .HorizontalSection:
return firstArray.count
case .VerticalSection:
return secondArray.count
default
return 0
}
}
In order to do this, you need to give your enum a type (Int in this case):
private enum TableSection: Int {
horizontalSection,
verticalSection
}
This makes it so that 'horizontalSection' will be assigned the value 0 and 'verticalSection' will be assigned the value 1.
Now in your numberOfRowsInSection method you need to use .rawValue on the enum properties in order to access their integer values:
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case TableSection.horizontalSection.rawValue:
return firstArray.count
case TableSection.verticalSection.rawValue:
return secondArray.count
default:
return 0
}
}
Jeff Lewis did it right, to elaborate on that and give the code litlle bit of more readiness -> my way of handling these things is to:
Instantiate enum with the raw value -> section index
guard let sectionType = TableSections(rawValue: section) else {
return 0
}
Use switch with section type
switch sectionType {
case .horizontalSection:
return firstArray.count
case .verticalSection:
return secondArray.count
}
Ok, I figured it out, thanks #tktsubota for pointing me in the right direction. I'm pretty new to Swift. I looked into .rawValue and made some changes:
private enum TableSections: Int {
case HorizontalSection = 0
case VerticalSection = 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case TableSections.HorizontalSection.rawValue:
return firstArray.count
case TableSections.VerticalSection.rawValue:
return secondArray.count
default
return 0
}
}
I am looking for a "good" way to solve some special requirements:
I have an UITableView with different sections, for example:
Base Data
About me
Interests
Images
Base Data contains always values (but there is still an variable row count) - and all other "Categories" could contain rows, or still could be empty. If there is no data, the category should be not shown.
No my first idea to solve that is:
Create all possible categories (but that could be 20 or more) - and do something like that:
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
var count:Int = 0
switch (section) {
case 0:
count = baseHeaders.count
case 1:
if(mapItem.courses?.count > 0) {
count = mapItem.courses!.count
}
break;
default:
count = 0
}
return count
}
And ill check also with: titleForHeaderInSection if the count is null, and return then no header for the section.
BUT: is that a good way? My concern is about creating 20 sections and just 2 are used. Is there another, better way? Can i create sections manually? If yes, should i? So that only the base category is visible, and append everything else if there is data available.
This looks like my way of approaching such problems. I'm using enums (Obj-C & especially Swift) to handle and identify my Sections and I always return the full amount of potential sections:
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return FormSection.count // enum function
}
In func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int, however, I switch the unused sections off by returning 0 rows.
The benefit I saw after struggling with your type of dynamic tables was that all sections are always at the same index which made cell management relatively easy:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let section:FormSection = FormSection(rawValue:indexPath.section)!
switch section {
case .Header:
//…
default:
//…
}
}
The same goes for section headers/footers:
override func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
switch section {
case FormSection.Header.rawValue:
return nil
case FormSection.RoomSetup.rawValue where foo == false:
return nil
default:
// return header with title = FormSection(rawValue: section)?.headerTitle()
// Swift enums ftw ;)
}
And the number of rows is calculated/fetched at runtime:
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let section:FormSection = FormSection(rawValue:section)!
switch section {
case .Section1:
return fooExpanded ? (numberOfFoo) : 0
case .Section2:
return model.barCount()
default:
return 1
}
}