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A global function calls a mutating method of a protocol type. How can I get rid of the var tmp object?


A global function calls a mutating method of a protocol type. How can I get rid of the var tmp object?

By : kramar42
Date : November 22 2020, 04:01 AM
this one helps. this is my working code snippet. But I want to get rid of the var tmp variable in the function slide. , It may work with this little change:
code :
func slide<M: Moveable>(slider: inout M) {
    slider.move(to: CGPoint(x: 100, y: 100))
}
slide(slider: &prius)
slide(slider: &square)


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Protocol Extension, Mutating Function

Protocol Extension, Mutating Function


By : Muhammad Rizwan
Date : March 29 2020, 07:55 AM
To fix the issue you can do If you intend to use the protocol only for classes then you can make it a class protocol (and remove the mutating keyword):
code :
protocol ColorImpressionableProtocol : class {

    // ...

    func adoptColorsFromImpresion(impresion: ColorImpressionableProtocol?)
}
init(impresion: ColorImpressionableProtocol?){
    super.init(nibName: nil, bundle: nil)
    adoptColorsFromImpresion(impresion)
}
Swift 2 Error using mutating function in Protocol extension "Cannot use mutating member on immutable value: 'self'

Swift 2 Error using mutating function in Protocol extension "Cannot use mutating member on immutable value: 'self'


By : Saucy Salamander
Date : March 29 2020, 07:55 AM
This might help you The problem is that, in the protocol you mark the function as mutating, which you need to do if you want to use the protocol on a struct. However, the self that is passed to testFunc is immutable (it's a reference to a instance of the class) and that is tripping up the compiler. This would make sense if testClass was actually a struct and you could make the function mutating to resolve the issue.
I can see two work arounds:
code :
protocol MTKAnimateValueDelegate: class { ...
func testFunc() {
    var animValue = MTKAnimateValue(fromValue: 10, toValue: 20, inSeconds: 2)
    animValue.isAnimating = true
    var mutableSelf = self
    mutableSelf.mtkAnimQueAppend(animValue) 
  }
Swift: Can't use mutating method in Protocol Extension

Swift: Can't use mutating method in Protocol Extension


By : Becgueule
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further I have a 4 view controllers that need to use a different image based on the user screen width. I am trying to keep the code DRY and use protocol extension. , This code:
code :
extension myViewController: ScreenSizeProtocolExt {    
let imageToUse = setupBG()
// Here is get an error: 'Use of instance member 'setupBG' on type 'inout Self'; did you mean to use a value of type 'inout self' instead?
let image = UIImage(named: imageToUse)
imageView.image = image    
}
let imageToUse = setupBG()
imageView.image = image 
python how to execute object method that calls a function which calls another method from same object

python how to execute object method that calls a function which calls another method from same object


By : Manik
Date : March 29 2020, 07:55 AM
it fixes the issue Use getattr() to get the class method to execute like:
Code:
code :
def start_party(party_participant, inner_function):
    print('♬♩♪♩')
    getattr(party_participant, inner_function)()
    print('♬♩♪♩')
class Feeling():
    def __init__(self):
        self.data_in = 'into connection'
        self.data_out = 'out of connection'


class Person():
    def __init__(self):
        self.feeling = Feeling()

    def execute(self, outer_function, inner_function):
        print(self.feeling.data_in)
        outer_function(self, inner_function)
        print(self.feeling.data_out)

    def dance(self):
        print(' └[∵┌]└[ ∵ ]┘[┐∵]┘ ')

    def sing(self):
        print('( ◜◒◝ )')


def start_party(party_participant, inner_function):
    print('♬♩♪♩')
    getattr(party_participant, inner_function)()
    print('♬♩♪♩')


liz = Person()
liz.execute(start_party, 'dance')
into connection
♬♩♪♩
 └[∵┌]└[ ∵ ]┘[┐∵]┘ 
♬♩♪♩
out of connection
Why does a mutating method in a Swift protocol infinitely recurse unless only an extension method?

Why does a mutating method in a Swift protocol infinitely recurse unless only an extension method?


By : Ilhom
Date : March 29 2020, 07:55 AM
like below fixes the issue With your change in the second example, by including the m in the protocol definition, that instructs Swift to employ dynamic dispatch. So when you call p.m(), it dynamically determines whether the object has overridden the default implementation of the method. In this particular example, that results in the method recursively calling itself.
But in the first example, in the absence of the method being part of the protocol definition, Swift will employ static dispatch, and because p is of type P, it will call the m implementation in P.
code :
protocol P {
    // func method()
}

extension P {
    func method() {
        print("Protocol default implementation")
    }
}

struct Foo: P {
    func method() {
        print(“Foo implementation")
    }
}
let foo: P = Foo()
foo.method()              // Protocol default implementation
protocol P {
    func method()
}
let foo: P = Foo()
foo.method()              // Foo implementation
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