I am trying to integrate this https://github.com/gareth-cross/kalman-ios project with my own Swift project in Xcode.
When building the project I receive 2 errors:
kalman-ios/matrix.hpp:28:10: error: 'cmath' file not found
failed to emit precompiled header
'/Users/.../Build/Intermediates.noindex/PrecompiledHeaders/Tron-iOS-Bridging-Header-
swift_J9ENU1M0P5CE-clang_M49XZJR5TLTE.pch'
for bridging header '/Users/.../Filter/Tron-iOS-Bridging-Header.h'
My project is purely Swift, and the kalman-ios project is a mixture of ObjC and ObjC++.
My bridging header file is:
//
// Use this file to import your target's public headers that you would like to expose to Swift.
//
#import "KFEstimator.h"
For more context, the kalman-ios project is structured as:
KFEstimator.mm makes calls to AttitudeESKF.cpp makes calls to matrix.cpp
My initial thought was the cmath file error was the cause for the bridging header error. But I have almost no experience outside Swift and don't know how to go about fixing it. Up until yesterday, I wasn't even aware that you could use ObjCPP.
Any help is appreciated!
I have solved the issue. I was mistaken and believed that the repository was Objective-C making calls to Objective-C++.
It was actually all Objective-C++.
I was able to make direct calls to the Objective-C++ functions by following this video guide.
i'm trying to add the SDK of google admob in my game but when i try to build the project after adding the admob sdk, i keep getting the error "Duplicate interface definition for class GADInterstitial"
However, when I do the same in a fresh project, I don't run into any issues at all. I have checked all the imports and project settings, they are all the same.
What should I look for, to resolve such an issue ?
You have two interfaces with the same name. Use Xcode's find in project menu option to find instances of "GADInterstitial".
Hope it will be help you.
The Objective-C #import pre-processor statement specifically ignores duplicate header files, unlike the C/C++ #include pre-processor statement (where it's necessary to use guard macros or #pragma once).
So I think you are using #include "GADInterstitial.h", instead of #import "GADInterstitial.h", somewhere in your source tree.
I'm trying to build a Cocoa Touch Framwork (XCode 6, obviously) with Objective-C and some Swift classes.
I've successfully added Swift classes to regular projects (no framworks) before so I'm aware of the build settings required for this (Embedded Content Contains Swift Code). Unfortunately, the framework project doesn't build the header file (projectName-Swift.h) and I'm not able to import the class and the Swift classes into any of my .m files.
Does anybody know why this wouldn't work, and what build settings I need to change in order to make this work?
Finally found the answer;
Within the frameworks the import statement for Swift files has to look as follows;
#import <ProjectName/ProjectName-Swift.h>
instead of
#import "ProjectName-Swift.h"
Sometimes it helps to RTFM (https://developer.apple.com/library/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html#//apple_ref/doc/uid/TP40014216-CH10-XID_82)
I've struggled with this for a while because I don't think the documentation is clear. I have a slightly different project setup, and it's taken me a while to work this out so I thought I'd answer here.
I have a project with name: MyProject
In this project, I have a framework: MyFramwork
I have a swift file in MyFramework which I want to import into an objective c file in MyFramework.
To do this, you need:
#import <MyFramework/MyFramework-Swift.h>
NOT
#import <MyProject/MyFramework-Swift.h>
Hope that helps someone.
I'm currently translating an Objective-C project I have over to Swift. In the process, I have a few implemented 3rd party libraries that are pure Objective-C like MFSideMenu and Parse.
I've created a Bridging-Header.h file per Apple's documentation and other's recommendations to bridge the Objective-C files with the Swift code. This works fine for frameworks like Parse. Unfortunately, when importing MFSideMenu and running the application, I receive the attached errors below.
I was contemplating if this was because a library needed to be manually imported into the Objective-C files using it, so I attempted importing UIKit and Foundation in the project and manually added the frameworks without any success. Any assistance would be greatly appreciated.
Turns out, the compiler for swift no longer supports non modular based imports for frameworks. You must change all references to frameworks to #import statements rather #import.
I had the same problem, add code below at the header file of this class
#import <UIKit/UIKit.h>
it can help you
I am playing around with some of the new iOS 7 features and working with some of the Image Effects as discussed in the WWDC video "Implementing Engaging UI on iOS". For producing a blur effect within the source code for the session, UIImage was extended via a category which imports UIKit like so:
#import UIKit;
I think I saw something about this in another session video but I'm having trouble finding it. I'm looking for any background information on when to use this. Can it only be used with Apple frameworks? Are the benefits of using this compiler directive enough that I should go back and update old code?
It's a new feature called Modules or "semantic import". There's more info in the WWDC 2013 videos for Session 205 and 404. It's kind of a better implementation of the pre-compiled headers. You can use modules with any of the system frameworks in iOS 7 and Mavericks. Modules are a packaging together of the framework executable and its headers and are touted as being safer and more efficient than #import.
One of the big advantages of using #import is that you don't need to add the framework in the project settings, it's done automatically. That means that you can skip the step where you click the plus button and search for the framework (golden toolbox), then move it to the "Frameworks" group. It will save many developers from the cryptic "Linker error" messages.
You don't actually need to use the #import keyword. If you opt-in to using modules, all #import and #include directives are mapped to use #import automatically. That means that you don't have to change your source code (or the source code of libraries that you download from elsewhere). Supposedly using modules improves the build performance too, especially if you haven't been using PCHs well or if your project has many small source files.
Modules are pre-built for most Apple frameworks (UIKit, MapKit, GameKit, etc). You can use them with frameworks you create yourself: they are created automatically if you create a Swift framework in Xcode, and you can manually create a ".modulemap" file yourself for any Apple or 3rd-party library.
You can use code-completion to see the list of available frameworks:
Modules are enabled by default in new projects in Xcode 5. To enable them in an older project, go into your project build settings, search for "Modules" and set "Enable Modules" to "YES". The "Link Frameworks" should be "YES" too:
You have to be using Xcode 5 and the iOS 7 or Mavericks SDK, but you can still release for older OSs (say iOS 4.3 or whatever). Modules don't change how your code is built or any of the source code.
From the WWDC slides:
Imports complete semantic description of a framework
Doesn't need to parse the headers
Better way to import a framework’s interface
Loads binary representation
More flexible than precompiled headers
Immune to effects of local macro definitions (e.g. #define readonly 0x01)
Enabled for new projects by default
To explicitly use modules:
Replace #import <Cocoa/Cocoa.h> with #import Cocoa;
You can also import just one header with this notation:
#import iAd.ADBannerView;
The submodules autocomplete for you in Xcode.
Nice answer you can find in book Learning Cocoa with Objective-C (ISBN: 978-1-491-90139-7)
Modules are a new means of including and linking files and libraries into your projects. To understand how modules work and what benefits they have, it is important to look back into the history of Objective-C and the #import statement
Whenever you want to include a file for use, you will generally have some code that looks like this:
#import "someFile.h"
Or in the case of frameworks:
#import <SomeLibrary/SomeFile.h>
Because Objective-C is a superset of the C programming language, the #import state‐ ment is a minor refinement upon C’s #include statement. The #include statement is very simple; it copies everything it finds in the included file into your code during compilation. This can sometimes cause significant problems. For example, imagine you have two header files: SomeFileA.h and SomeFileB.h; SomeFileA.h includes SomeFileB.h, and SomeFileB.h includes SomeFileA.h. This creates a loop, and can confuse the coimpiler. To deal with this, C programmers have to write guards against this type of event from occurring.
When using #import, you don’t need to worry about this issue or write header guards to avoid it. However, #import is still just a glorified copy-and-paste action, causing slow compilation time among a host of other smaller but still very dangerous issues (such as an included file overriding something you have declared elsewhere in your own code.)
Modules are an attempt to get around this. They are no longer a copy-and-paste into source code, but a serialised representation of the included files that can be imported into your source code only when and where they’re needed. By using modules, code will generally compile faster, and be safer than using either #include or #import.
Returning to the previous example of importing a framework:
#import <SomeLibrary/SomeFile.h>
To import this library as a module, the code would be changed to:
#import SomeLibrary;
This has the added bonus of Xcode linking the SomeLibrary framework into the project automatically. Modules also allow you to only include the components you really need into your project. For example, if you want to use the AwesomeObject component in the AwesomeLibrary framework, normally you would have to import everything just to use the one piece. However, using modules, you can just import the specific object you want to use:
#import AwesomeLibrary.AwesomeObject;
For all new projects made in Xcode 5, modules are enabled by default. If you want to use modules in older projects (and you really should) they will have to be enabled in the project’s build settings. Once you do that, you can use both #import and #import statements in your code together without any concern.
#import Module(ObjC) or Semantic import
instead of usual module using
//as example
#include <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
History:
[#include -> #import] -> [Precompiled Headers .pch] -> #import Module(ObjC); -> [import Module(Swift)]
It is a part of LLVM Modules
#import <module_name>; declaration says to compiler to load(instead of compile) a precompiled binary of module which decrease a building time. Previously compiler compiled dependency every time when runt into it but now it should be compiled beforehand and just loaded
//previously
run into dependency -> compile dependency
run into dependency -> compile dependency
//#import
compile dependency
run into dependency -> load compiled binary
run into dependency -> load compiled binary
[Modulemap] - bridge between module and headers
Xcode
Enable Modules(C and Objective-C)(CLANG_ENABLE_MODULES) - CLANG #include, #import directives are automatically converted to #import that brings all advantages. Modulemap allows to do it seamless because contains a map between headers and sub/modules
Pass -fmodules
#include, #import -> #import
Link Frameworks Automatically(CLANG_MODULES_AUTOLINK) - enables system modules auto linking. Requires activated CLANG_ENABLE_MODULES. Auto-linking allows to pass -framework <framework_name> based on #import, #import(Objective-C), import(Swift)
If NO - passes -fno-autolink flag
CLANG_ENABLE_MODULES == NO and CLANG_MODULES_AUTOLINK == NO
If you want to handle system(#import <UIKit/UIKit.h>) linking manually(instead of auto-linking) you have two variants:
Add dependency into General -> Frameworks and Libraries or Frameworks, Libraries, and Embedded Content
Build Settings -> Other Linker Flags(OTHER_LDFLAGS) -> -framework <module_name>
Next error will be thrown if:
Undefined symbol: _OBJC_CLASS_$_UIView
Undefined symbols for architecture x86_64:
"_OBJC_CLASS_$_UIView", referenced from:
objc-class-ref in ClassB.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1
CLANG_ENABLE_MODULES is disabled
CLANG_MODULES_AUTOLINK is disabled and no manual linking
Reverse engineering
otool -l <binary>
//-l print the load commands
//find LC_LINKER_OPTION
//cmd LC_LINKER_OPTION
It currently only works for the built in system frameworks. If you use #import like apple still do importing the UIKit framework in the app delegate it is replaced (if modules is on and its recognised as a system framework) and the compiler will remap it to be a module import and not an import of the header files anyway.
So leaving the #import will be just the same as its converted to a module import where possible anyway
It seems that since XCode 7.x a lot of warnings are coming out when enabling clang module with CLANG_ENABLE_MODULES
Take a look at Lots of warnings when building with Xcode 7 with 3rd party libraries
There is a few benefits of using modules. You can use it only with Apple's framework unless module map is created. #import is a bit similar to pre-compiling headers files when added to .pch file which is a way to tune app the compilation process. Additionally you do not have to add libraries in the old way, using #import is much faster and efficient in fact. If you still look for a nice reference I will highly recommend you reading this article.