类型“myViewController”不符合Swift中的协议UIPIckerDataSource

Question

I just create a new class in Swift, it's called myViewController and it's a UIViewController . Now I'm trying to make it a UIPickerViewDelegate and DataSource but i got a strange error

import UIKit

class myViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
   ...
}

It says Type "myViewController" does not conform to protocol UIPIckerDataSource over the UIPickerViewDataSource.

Is it a bug of Xcode-Beta 3??

Answer 1

You need to implement all the required methods of UIPickerViewDataSource and UIPickerViewDelegate , if you want to conform to these protocols.

Swift is more like java when it comes to protocols because if you don't implement all the required methods declared by a protocol you are going to get a compile time error instead of a run time exception.

Answer 2

Fix-it in XCode 8.1 inserts a deprecated version of the method below if you're using Swift 3:

func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
    return componentNumber
}

In XCode 10.0+

func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return componentNumber
}

Answer 3

Implement required method of UIPickerDataSource as in documentation.

The data source provides the picker view with the number of components, and the number of rows in each component, for displaying the picker view data. Both methods in this protocol are required.

So you need to implement these methods

func numberOfComponentsInPickerView(_ pickerView: UIPickerView!) -> Int {}

   func pickerView(_ pickerView: UIPickerView!,
numberOfRowsInComponent component: Int) -> Int{}

Answer 4

My problem was that I had override in front of the implementation function, where Swift doesn't consider protocol method implementations to be overrides ( same ). Just taking out the override keyword fixed the issue.

Answer 5

My problem is protocol's method name is illegal,

@protocol ContactsSelectDelegate <NSObject>

- (void)selectContacts:(NSMutableArray *)contacts Tags:(NSMutableArray *)tags;

@end

Here, Tags: should be tags: .
I hope my answer is helpful.