I am using a third party library (https://github.com/zhang28602/ZZYQRCode) for my project. When I indergrated it into my project it started throwing the following error: Typedef redefinition with different types ('void (^)(NSString *__strong)' vs 'void (^)(__strong id, NSURLResponse *__strong)')
for the following line of code: typedef void(^SuccessBlock)(NSString *reuslt);
Please help me resolve this.
That project has defined a global typedef in its public header using a very generic name (SuccessBlock). You likely have defined SuccessBlock in another way somewhere else in your program.
If possible, have the developer use prefixes on their names. This should have been ZZYSuccessBlock. Alternately, rename the other instance of SuccessBlock.
If that's not possible, try to ensure that no part of your system imports both ZZYQRCode.h and whatever .h file defines the other version of it.
Related
OBJ-C ONLY...
That is,
An ObjC app imports ObjC static lib A.
Static lib A imports static lib B.
Static lib A has functions that call functions within lib B.
The app only calls functions in lib A and does not call functions in lib B.
Can I assume that lib A or B can be either Obj-C or Swift?
IE. Can an ObjC app import an ObjC-or-Swift static lib A that itself imports a second ObjC-or-Swift static lib B? (yes, 4 use case permutations)
the git repository https://github.com/CombineCppSwiftObjcInStaticLib i created for you is showing this..
your initial #objc func run_central() in BLE_central.swift is exposed, which triggers the precompiler to generate objc compatible headers (bridge) which then again makes it possible to call the function from a method inside .mm(objc++) or .m(objc) when this generated header is imported.
In fact Hub_lib inside the repo is a static ObjC++ lib mixed with Swift. It would work the other way around also. The headers are the key for success here. If you can provide some objc or c or c++ header to swift functions it becomes compatible and wise versa. I mean in general, thats the idea of headers. If you don't have headers, that does not mean you can not call some external stuff, it just means you would call it blind. A proper IDE will complain before you even try to do this evil stuff, unknown entry points aka unknown symbols etc.. So you go for a proper header - always.
To properly combine swift with other languages its good to know there are always two ways of bridging.
In case of Objective-C (and also Objective-C++) it is
Bridging into Swift (projectname-Bridging-Header.h),
and Bridging out of Swift (expose with #objc to trigger automatically internal generation of projectname-Swift.h file. So this header is "invisible" in the file browser on the left side. Nor will you find it in the repo as file, it is named by modulename which is the project-name). The last mentioned header you could even write manually yourself, with lots of troublesome back-draws.
Hint: Executable code is executable code. No matter what language, as far it is compiled for the right device architecture and has symbols to call and you know what to do with the data returned.
Another Hint: there is a way to handle C pointers in swift see docu which become swift datatypes which you can use to go the other way and declare functions to return those from swift.
And direct use of C in Swift is also possible. The compiler considers if you explicit mark some code as C. extern "C" { /* code */ } will cause the C++ compiler to remember, this is still C++ code to compile the function in such a way, it can be called from C (and Swift)
//Example.hpp //no target membership
#ifdef __cplusplus
#include <stdio.h>
class Example {
private:
const char * _name;
public:
Example(const char *name);
~Example(void);
int getLen(void);
};
#endif
There should be an Example.cpp and don't forget to tell Xcode you deal with c++ #ifdef __cplusplus + #endif
//Example.cpp //has target membership
#include "Example.hpp"
#ifdef __cplusplus
#include <stdio.h>
#include <string>
//code implementation according to example.hpp
Example::Example(const char *name) {
_name = name;
}
int Example::getLen() {
return (int)strlen(_name);
}
#endif
//ExampleWrapper.cpp //has target membership
#include "Example.hpp" //c++ header file
extern "C" int myCppFunction(const char *s)
{
// Create an instance of Example, defined in the library
// and call getLen() on it, return result.
return Example(s).getLen();
}
So this function needs to be declared in the bridging header to make use of it.
//
// Use this file to import your target's public headers that you would like to expose to Swift.
//
// for extern "C" functions declare them one by one here
// as implemented in ExampleWrapper.cpp
// becomes "func myCppFunction(_ s: UnsafePointer<Int8>!) -> Int32" in swift
int myCppFunction(const char * s);
and then call from swift..
os_log("The result from C++ is %u", myCppFunction("12345"))
So in fact, yes. Integrating a static lib A that calls static lib B in App is possible. Happy compiling as long you offer some header for each part that needs to know what is inside the head of the other lib. That is true for Apps as it is true for libs and frameworks under each other.
Edit here some important stuff to read about Swift Package Manager C support https://github.com/apple/swift-evolution/blob/master/proposals/0038-swiftpm-c-language-targets.md
As long as the libraries export Objective-C compatible symbols, it doesn't matter if they're written in Objective-C, or Swift, or C++, or any other compiled language.
And we know that the Swift compiler exports Objective-C compatible symbols for all declarations that are marked with #objc (either explicitly or implicitly).
From a consumer perspective it doesn't matter which language generated the libraries, as long as the Objective-C compiler/linker can consume the symbols exported by those libraries.
I'm getting this error:
/Class/GData/OAuth/GDataOAuthViewControllerTouch.m:116:22: Expected a type
That line is:
authentication:(GDataOAuthAuthentication *)auth
Inside of this block of code:
- (id)initWithScope:(NSString *)scope
language:(NSString *)language
requestTokenURL:(NSURL *)requestURL
authorizeTokenURL:(NSURL *)authorizeURL
accessTokenURL:(NSURL *)accessURL
authentication:(GDataOAuthAuthentication *)auth
appServiceName:(NSString *)keychainAppServiceName
delegate:(id)delegate
finishedSelector:(SEL)finishedSelector {
NSString *nibName = [[self class] authNibName];
I'm a newb XCode developer. So far I've created and compiled a calculator app based from an online class but that's it.
Is this a library that is not being included?
Background: The previous developer abandoned the project and the owner sent the project code to me. I'm trying to replace the existing graphics with new graphics and recompile it with support for iOS 6, which I thought I should be able to do without any coding, but have run into this error and many others when I opened the project. I have the latest XCode.
The :22 (and the position of the caret within the editor) tell you exactly where on the line the error is. In this case it's telling you that where it sees GDataOAuthAuthentication it was expecting a type. So, implicitly, it doesn't recognise that GDataOAuthAuthentication is a type.
Objective-C still sits upon compilation units ala C — each .m file is compiled in isolation then the lot are linked together. You use #import (or #include if you want; #import just guarantees the same file won't be included twice) to give each individual file visible sight of any external definitions it needs.
So, that's a long-winded way of reaching the same conclusion as Rick did five minutes ago: you've probably omitted a necessary #import.
A few things to look for:
Did you #import the file where the GDataOAuthAuthentication type is defined? (e.g. #import "GDataOAuthAuthentication.h")
Is there a variable named GDataOAuthAuthentication which is causing the compiler to think GDataOAuthAuthentication is a variable not a type?
I'm attempting to follow along with the RestKit unit test guide ( https://github.com/RestKit/RestKit/wiki/Unit-Testing-with-RestKit ) except that my project is a static library instead of an app.
Here is the test I've written:
- (void)testMappingOfDate
{
id parsedJSON = [RKTestFixture parsedObjectWithContentsOfFixture:#"plan.json"];
RKMappingTest *test = [RKMappingTest testForMapping:[self planMapping] object:parsedJSON];
[test expectMappingFromKeyPath:#"plan.date" toKeyPath:#"date"];
STAssertNoThrow([test verify], nil);
}
When I attempt to run the test I receive this error on the first line of the test:
error: testMappingOfDate (api_clientTests) failed: -[NSBundle parsedObjectWithContentsOfResource:withExtension:]: unrecognized selector sent to instance 0x1765c40
It seems like its not finding the NSBundle category defined by RestKit, but my test target header search path is set to "$(BUILT_PRODUCTS_DIR)/../../Headers" and I've verified this path includes NSBundle+RKAdditions.h which contains the supposed "unrecognized selector".
Is there something I'm missing here?
You are trying to include a category within your binary that comes from a library. To get that accomplished you will need to add the following to your (Unit-Test-Target's) build settings.
Other Linker Flags: -ObjC
From Apple's QA:
Objective-C does not define linker symbols for each function (or
method, in Objective-C) - instead, linker symbols are only generated
for each class. If you extend a pre-existing class with categories,
the linker does not know to associate the object code of the core
class implementation and the category implementation. This prevents
objects created in the resulting application from responding to a
selector that is defined in the category.
Solution:
To resolve this issue, the static library should pass the -ObjC option
to the linker. This flag causes the linker to load every object file
in the library that defines an Objective-C class or category. While
this option will typically result in a larger executable (due to
additional object code loaded into the application), it will allow the
successful creation of effective Objective-C static libraries that
contain categories on existing classes.
The error means that the "unrecognized selector" issue is at runtime. The compiler and NSBundle+RKAdditions.h do not give this error they would at compile timr.
The issue is that the code that has #implementation NSBundle(RKAdditions) is not linked into your app. So you need to add this to your build
I am finally trying to convert my ios project to ARC. there is several files that I do not want to convert to ARC, so I have added the "-fno-objc-arc" flag to build phase -> compile sources to the corresponding *.m file.
However, when I try to edit -> refactor -> convert to ARC, I am getting a "Cannot Convert to Objective-C ARC: Xcode found 3 issues that prevent conversion from proceeding. Fix all ARC readiness issues and try again." error
the errors are all on the *.h file for which I have added the -fno-objc-arc to for the corresponding *.m file... Do I have to add the flag to the *.h file too? If so, where can I find it?
Thanks!
EDIT So I read the error more clearly. the file i am having issue with is JSONKit.h. The errors are not generated in JSONKit.m, but other classes that I wrote which imports JSONKit.h So is the only solution to add the -fno-objc-arc flag to my own classes that imports JSONKit.h? Thanks
temporary getaround (unless someone can suggest better)
I have having error with the following in JSONKit.h
typedef struct {
JKParseOptionFlags parseOptionFlags;
JKConstBuffer stringBuffer;
size_t atIndex, lineNumber, lineStartIndex;
size_t prev_atIndex, prev_lineNumber, prev_lineStartIndex;
int errorIsPrev;
JKParseToken token;
JKObjectStack objectStack;
JKTokenCache cache;
JKObjCImpCache objCImpCache;
NSError *error;
} JKParseState;
the error is on the NSError line - "ARC forbids Objective-C objects in structs or unions"
following another stackoverflow question, I changed the line to
__unsafe_unretained NSError *error;
and it compiles... seems to work ok so far
I'm trying to assign a function to the AURenderCallback inputProc
int setupRemoteIO(audio unit etc){
inProc.inputProc = playerCallback
}
but it says that playerCallback is not declared in this scope although playerCallback is present in the same file and class as setupRemoteIO.
The player callback is like this
static OSStatus playerCallback(void *inRefCon etc)
What could be the problem?
In C, you need to declare a function before its first use, i.e. higher up in the file than the point where you try to use the function. That's why include files are usually clustered at the top of a file; all of the symbols declared in the headers will be available throughout the code in the including file.
In this case, that means the declaration of your callback:
static OSStatus playerCallback(void *inRefCon etc);
must appear before your setupRemoteIO() function so that the compiler knows the function exists when you come to use it.
As you're on iOS, I'll also make the point that in recent compilers this restriction doesn't apply to Objective-C methods. It used to: you could only use method selectors that had already been seen. But in newer versions of Clang an Objective-C method can make use of a selector declared later in the same file without error.