Apple's Swift compiler complains of partial application when creating extension method on Array
To use an operator as a function, surround it in parens:
var min = array.comparest({ $0 }, (<))!
For example:
[1,2,3].reduce(0,(+)) // -> 6
Can't create default closure parameter in Array extension method in Swift
The elements in an array don't have to be Comparable
, which means you can't write that function for all possible Arrays.
Unfortunately Swift doesn't allow you to extend just a subset of Arrays. In other for your function to work, the compiler needs extra type information to infer the type C
.
Others have struggled with this same issue:
How can we create a generic Array Extension that sums Number types in Swift?
Instead of using an extension, you should be able to use minimum
as a global function.
What alternative when I get: Partial application of 'mutating' method is not allowed
One way is to accept an inout Test
in technique
. Also you should make apply
mutating
, because it undoubtedly changes the state of Test
.
mutating func apply(technique: (inout Test, Int) -> ()) {
print("Before:\(value)")
technique(&self, 2) // this is "kind of" analogous to "self.technique(2)"
print("After:\(value)")
}
mutating func main() {
apply(technique: {
$0.increment(amount: $1)
})
}
Compiler complains that 'Expression resolved to unused function' when removing index in array of functions
Resolving to an unused function
is trying to tell you that you have an expression that is returning a function type, but you never call it
So,you just need try to use it
typealias Type1 = Int
typealias Type2 = ([AnyObject?]) -> Void
class Test {
private var cb1: [Type1]
private var cb2: [Type2]
init() {
cb1 = [Type1](count: 2, repeatedValue: 0)
cb2 = [Type2](count: 2, repeatedValue: { _ in })
}
func removeAtIndex(index: Int) {
cb1.removeAtIndex(index)
let result = cb2.removeAtIndex(index)
}
}
Compiler complains that 'Expression resolved to unused function' when removing index in array of functions
Resolving to an unused function
is trying to tell you that you have an expression that is returning a function type, but you never call it
So,you just need try to use it
typealias Type1 = Int
typealias Type2 = ([AnyObject?]) -> Void
class Test {
private var cb1: [Type1]
private var cb2: [Type2]
init() {
cb1 = [Type1](count: 2, repeatedValue: 0)
cb2 = [Type2](count: 2, repeatedValue: { _ in })
}
func removeAtIndex(index: Int) {
cb1.removeAtIndex(index)
let result = cb2.removeAtIndex(index)
}
}
Overriding methods in Swift extensions
Extensions cannot/should not override.
It is not possible to override functionality (like properties or methods) in extensions as documented in Apple's Swift Guide.
Extensions can add new functionality to a type, but they cannot override existing functionality.
Swift Developer Guide
The compiler is allowing you to override in the extension for compatibility with Objective-C. But it's actually violating the language directive.
That just reminded me of Isaac Asimov's "Three Laws of Robotics" /p>
Extensions (syntactic sugar) define independent methods that receive their own arguments. The function that is called for i.e. layoutSubviews
depends on the context the compiler knows about when the code is compiled. UIView inherits from UIResponder which inherits from NSObject so the override in the extension is permitted but should not be.
So there's nothing wrong with grouping but you should override in the class not in the extension.
Directive Notes
You can only override
a superclass method i.e. load()
initialize()
in an extension of a subclass if the method is Objective-C compatible.
Therefore we can take a look at why it is allowing you to compile using layoutSubviews
.
All Swift apps execute inside the Objective-C runtime except for when using pure Swift-only frameworks which allow for a Swift-only runtime.
As we found out the Objective-C runtime generally calls two class main methods load()
and initialize()
automatically when initializing classes in your app’s processes.
Regarding the dynamic
modifier
From the Apple Developer Library (archive.org)
You can use the dynamic
modifier to require that access to members be dynamically dispatched through the Objective-C runtime.
When Swift APIs are imported by the Objective-C runtime, there are no guarantees of dynamic dispatch for properties, methods, subscripts, or initializers. The Swift compiler may still devirtualize or inline member access to optimize the performance of your code, bypassing the Objective-C runtime. /p>
So dynamic
can be applied to your layoutSubviews
-> UIView Class
since it’s represented by Objective-C and access to that member is always used using the Objective-C runtime.
That's why the compiler allowing you to use override
and dynamic
.
Swift crash report function signature specialization Owned To Guaranteed
I suspect the
registeredContacts
comment (added by HockeyApp I believe) is not relevant here
No, I think you have it backwards. That is exactly what is relevant. It is your crash report that is not relevant.
SIGTRAP merely means that we got an exception. The exception is being thrown in the code (or rather, in the course of executing the code). But you don't seem to be getting any info as to what it is. My guess is that HockeyApp is actually interfering with your receiving the real report, which would tell you what the exception was.
The problem is thus somewhere in retrieveActivities
. You might try to guess where by counting lines (you are told the number of lines into your method where the crash actually happens). It could be something as simple as out-of-bounds array access, I believe. The fact that an array registeredContacts
is popping up here is thus quite suggestive. Look for a registeredContacts
access at about that point in the method.
Command failed due to signal: Segmentation fault: 11
For anyone else coming across this... I found the issue was caused by importing a custom framework, I have no idea how to correct it. But simply removing the import and any code referencing items from the framework fixes the issue.
(╯°□°)╯︵ ┻━┻
Hope this can save someone a few hours chasing down which line is causing the issue.
Related Topics
Extract Reality Composer Scene for Arquicklook
How to Build a Recursive Function in Swift to Return a String
Applescript Email Attachment Not Working in Handler
Public Default Init in Protocol
How to Specify The Name of The Output Executable
Querying Geohashes in Firestore Returns Nothing
Parse Weird Bug in Swift That Causes Acl Write Permissions to Change to an Objectid
Getting The Parameterised Type of a Generic in Swift
Difference Between Any? and Any
Swift: Tvos Ibaction for UIcontrol in Collection View Cell Never Gets Called
Swift Set UIbutton Setbordercolor in Storyboard
How to Enable a Button in Different Cases in Swift
My UIcollectionview Does Not Scroll Smoothly Using Swift
Dynamic Links Firebase Function Not Being Called at All Xcode 12
Cropping Cgrect from Avcapturephotooutput (Resizeaspectfill)
Could Not Find an Overload for "Init" That Accepts The Supplied Arguments (Swift)