I am trying to run unit test whereby I am getting an warning:
'FileName' may not respond to '-failWithException:'
I wanted to know why this warning occurs and how to fix that?
Either the FileName interface does not declare the failWithException: method, or you have not imported the header file in which the interface is declared.
Whatever sort of object FileName is, the compiler can't find a method named '-failWithException' in that class. The solution is to go implement that method on that class, or to make sure the compiler can find the header file where it already is implemented.
By the way, it's a warning instead of an error because, unlike for instance Java, Objective-C allows you to manipulate classes at runtime. So while you PROBABLY have a problem there, you don't DEFINITELY have a problem, so the IDE gives you a yellow warning rather than a red error. But in your case, this is almost certainly something you need to fix.
Related
I'm using GWT 2.9 with elemental2-1.0.0-RC1.
The following code throws a ClassCastException at runtime:
DocumentRange documentRange = Js.cast(DomGlobal.document); // Fails
Range range = documentRange.createRange(); // Never reaches here
When I change to use an Js.uncheckedCast() instead, it succeeds:
DocumentRange documentRange = Js.uncheckedCast(DomGlobal.document);
Range range = documentRange.createRange(); // Works
The documentation for Js.uncheckedCast() says:
"You should always prefer regular casting over this (unless you know what you are doing!)."
I don't know why I'm having to use it, so I'm feeling nervous. Can someone explain how Js.cast() performs its type-checking and why I need to use an Js.uncheckedCast() in this instance?
Js.cast() is a way to cheat a bit, and do something that the Java language will not permit, but might actually be legal. Ignoring "how it actually works", the idea is that you can now get past issues where Java would complain, even if it turns out to be legit.
An example could be where you take a java.lang.Double or double and want to treat it as a JsNumber so you can call toPrecision(2) on it. Since java.lang.Double is final, it isn't legal to cast to an unrelated type, but Java doesn't know that in GWT, Double is really just a js Number. So, instead you can perform the cast with Js.cast(). The compiler will insert a runtime type check in there, verifying at runtime that your number is in fact a JS Number instance.
Another example could be trying to extend some native type that elemental2 provides, either to implement a workaround for a missing feature, or to do something browser-specific. Your new class may not extend the existing class - from JS's perspective this is okay, you are just describing the API that you know will exist at runtime. As such, we need to avoid the Java language check of "does this cast even make sense?", and just tell the compiler to try it.
On the other hand, you can "lie" to the compiler with Js.uncheckedCast(). This is used in cases where you are even asking the runtime to skip the check, and just pretend that it will work. This can let you do weird things, like treating Strings as if they were arrays, or solve cross-frame problems. No runtime check will be emitted, so instead you might just get a TypeError if a method/property is missing, instead of a proper ClassCastException.
In elemental2-dom 1.0.0-RC1, there is a class called DocumentRange, but it doesnt really make any sense - it is declared as a class, which means it can be type checked in JS, but the browser spec says that it should be an "interface" (which in JS-land means that it just is a description of a type, rather than something you can typecheck). https://www.w3.org/TR/DOM-Level-2-Traversal-Range/ranges.html#Level2-DocumentRange-method-createRange
This bug is inherited from closure-compiler, which claims that this has a constructor: https://github.com/google/closure-compiler/blob/6a418aa/externs/browser/w3c_range.js#L241-L251
The fix is for closure-compiler to refer to this as an interface, and for a new release of elemental2 to be made so you can use this.
There are two workarounds you can make here. The first is to cheat with Js.uncheckedCast(DomGlobal.document) and say "yes, I know that the Document is not instanceof DocumentRange, but that's because there is no such class as DocumentRange, so just pretend it worked so I can call createRange() on it". This is what you are doing already - it hides the fact there is a bug, but at the end of the day it works.
The "correct" answer is to declare your own DocumentRange, and do a Js.cast() to that instead. This is still gross - you have to keep your new interface around until closure gets fixed, and then elemental2 gets released, and then you have to remember to clean it up.
In this case, I would suggest lying to GWT and using Js.uncheckedCast() - there is only a single method on here, and it is unlikely to change in a meaningful way.
In Swift 3.0, the automated changing of function names due to the "Omit Needless Words" rule has caused two functions in an ObjC class to be the same.
- (void)showLoader;
...and...
- (void)show __deprecated_msg("User 'showLoader'");
The problem is that these functions are within a third party Cocoa Pod (otherwise I would just delete the unnecessary 'show' function).
This results in getting the error "Ambiguous use of 'show'" when I try to invoke the function like this:
loader?.show()
Is there a way to reverse the automatic changing of function name in Swift 3.0 or to help the compiler know which function I want to invoke?
Thanks for your help!
See MartinR's answer to my similar question here: Converting to Swift 3 renamed my own Objective-C method
If you owned the code, you could use NS_SWIFT_NAME(showLoader()) after your method declaration to force the ObjC-to-Swift method conversion to be named what you want:
- (void)showLoader NS_SWIFT_NAME(showLoader());
I think it's worth mentioning even though in your case it doesn't exactly solve your problem because you don't own the code.
You can work around this by calling
loader?.perform(Selector("showLoader"))
You will see a warning from the compiler, but it will compile successfully, and things will work correctly at runtime.
I'm using a SDK in one of my projects and when adding in the libraries etc, I get an error from this line of code, which is from inside a .h file. I cannot change the .m since its not available to me. Its inside .a (lib)
-(enum scanDeviceID)ID;
And the error message is:
Semantic Issue
ISO C++ forbids forward references to 'enum' types
Are there any compilier/build setting that I can modify to make this work?
Failing that, I know very little C++, is there something on the line of code I can change to make it work?
The line of code says that this method returns an element that's named in the scanDeviceID enum. The problem is that the compiler doesn't see a declaration of that enum. Somewhere in a .h file you should have that declaration. Importing the file should fix it.
I've got a C++ class I want to use which has all the code in the header file, rather than the CPP file. I'm trying to call it from an objective-C file which inherits a UIViewController class. I've renamed the file to .mm and imported the header file for the C++ file. When I compile, I keep getting a compile-time error when I try and access a method from the C++ class saying Request for member '<method>' in '<objectName>' which is of non-class type '<C++ class name>'. I did a search and it seemed that the header was usually the issue, but I've included the header in my file. What else could it be? (I can include generic code if required, but the I'm not sure if I'm allowed to show the actual code since it belongs to a third party).
The problem is likely in the declaration of the object that gives you the error, not in the header file. Sometimes the problem is hard to spot, you'll have to share some code if you can't figure it out by yourself.
I'm not a C++ coder, so this was probably an obvious mistake, but if anyone else comes across a similar problem, I simply changed my code from:
myObject.method();
to
myObject->method();
I'm working on a Perl module and whenever I call the skip() method I wrote in the following way:
$cursor->skip(4);
I get:
Undefined subroutine &MyModule::Cursor::skip called at t/tester.pl line 24.
(in cleanup) invalid object at t/tester.pl line 24.
When I call it like:
MyModule::Cursor::skip($cursor, 4);
Perl finds it!
Oddly, if I name "skip" anything else ("skipper", "hello"), this syntax works:
$cursor->skipper(4);
I thought maybe skip() was a "secret" reserved key word or something, but I've also got methods named sort() and next() (which I know are reserved), and those work fine.
I'd really like to name this method "skip." Does anyone know why Perl can't find it?
skip() is exported from Test::More, which you might have loaded since your executable is named t/tester.pl.
What does ref($cursor) yield you? It should be a blessed MyModule::Cursor object, but the "invalid object" error might be suggesting the object was not constructed properly.
EDIT: perldiag gives another clue: "in cleanup" signifies that a problem was encountered by the object's destructor. Assuming you don't already have a destructor in the object, create a MyModule::Cursor::DESTROY method that Data::Dumps the object to see what it looks like at this time.
A concise snippet of example code that exhibits this behaviour would be very helpful.
Without actual code, it's difficult to debug this.
Do you use MyModule::Cursor in your test code? When you replaced skip with skipper, were you calling it in exactly the same way from your test module? Are you able to use skip from a throw-away (one-liner or very short script)?
Where I'm going with this is looking for an error in your test code, rather than the module.
UPDATE: You're not doing something like declaring methods on MyModule::Cursor in two different files, are you? The error message you're getting tells me it has a blessed reference to an object of type MyModule::Cursor, so it knows about the class; but then it can't find the definition of skip. Do you happen to declare part of MyModule::Cursor in one file, and skip in another, and your test module isn't including the second file? Or do you have a syntax error somewhere around your definition of skip -- a missing semi-colon or unpaired curly brace? (But then again, why would MyModule::Cursor::skip work where $cursor->skip does not?)