Question

我在Cocoa应用程序中使用一个小型C ++库（atm只是一个非常简单的例子来了解我应该怎么做）。

所以我在命名空间中有一个小的C ++类，如下所示：

namespace testlib {
class Test {
public:
    Test(unsigned a);
    Test operator+(const Test& other) const;
    Test operator+(unsigned other) const;
    Test& operator+=(unsigned other);
    Test& operator+=(const Test& other);
    unsigned getValue() const;
private:
    unsigned theValue;
};
}

然后我有一个带有以下代码的.h文件：

#import <Foundation/Foundation.h>
#import "testlib.h"

@interface test : NSObject {
     testlib::Test* testClass;
}

- (id)init;
- (id)add: (unsigned)value;
- (unsigned)value;
- (void)dealloc;

@property void* testClass;

@end

最后是一个实现（在一个名为test.mm的文件中）：

#import "test.h"

@implementation test

@synthesize testClass;

- (id)init {
 testClass = new testlib::Test(0);
 return self;
}

- (void)dealloc {
 delete testClass;
 [super dealloc];
}

- (id)add: (unsigned)value {
 *testClass += value;
 return self;
}

- (unsigned)value {
     return testClass->getValue();
}

当我尝试编译时，我得到了以下错误：

CompileC build/testipod.build/Debug-iphonesimulator/testipod.build/Objects-normal/i386/WindowController.o WindowController.m normal i386 objective-c com.apple.compilers.gcc.4_2
 cd /Users/sausalito/eth/testipod
 setenv LANG en_US.US-ASCII
 setenv PATH "/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 -x objective-c -arch i386 -fmessage-length=0 -pipe -std=c99 -Wno-trigraphs -fpascal-strings -fasm-blocks -O0 -Wreturn-type -Wunused-variable -D__IPHONE_OS_VERSION_MIN_REQUIRED=30000 -isysroot /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator3.1.3.sdk -fvisibility=hidden -mmacosx-version-min=10.5 -gdwarf-2 -iquote /Users/sausalito/eth/testipod/build/testipod.build/Debug-iphonesimulator/testipod.build/testipod-generated-files.hmap -I/Users/sausalito/eth/testipod/build/testipod.build/Debug-iphonesimulator/testipod.build/testipod-own-target-headers.hmap -I/Users/sausalito/eth/testipod/build/testipod.build/Debug-iphonesimulator/testipod.build/testipod-all-target-headers.hmap -iquote /Users/sausalito/eth/testipod/build/testipod.build/Debug-iphonesimulator/testipod.build/testipod-project-headers.hmap -F/Users/sausalito/eth/testipod/build/Debug-iphonesimulator -F/Users/sausalito/eth/testipod/../testlib/build -I/Users/sausalito/eth/testipod/build/Debug-iphonesimulator/include -I/Users/sausalito/eth/testipod/build/testipod.build/Debug-iphonesimulator/testipod.build/DerivedSources/i386 -I/Users/sausalito/eth/testipod/build/testipod.build/Debug-iphonesimulator/testipod.build/DerivedSources -include /var/folders/4f/4fSYMOmtHHSRoBf+XVFQ+k+++TM/-Caches-/com.apple.Xcode.502/SharedPrecompiledHeaders/testipod_Prefix-cwdputxcxpofoydkulngkdplqxbt/testipod_Prefix.pch -c /Users/sausalito/eth/testipod/WindowController.m -o /Users/sausalito/eth/testipod/build/testipod.build/Debug-iphonesimulator/testipod.build/Objects-normal/i386/WindowController.o

 In file included from /Users/sausalito/eth/testipod/Classes/test.h:10,
             from /Users/sausalito/eth/testipod/WindowController.m:10:
/Users/sausalito/eth/testipod/Classes/testlib.h:1: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'testlib'
 In file included from /Users/sausalito/eth/testipod/WindowController.m:10:
/Users/sausalito/eth/testipod/Classes/test.h:13: error: expected specifier-qualifier-list before 'testlib'

/Users/sausalito/eth/testipod/Classes/test.mm:13:0 /Users/sausalito/eth/testipod/Classes/test.mm:13: error: type of property 'testClass' does not match type of ivar 'testClass'

我做错了什么？看起来它使用C编译器来编译头文件。

当我将成员声明为void *类型然后在实现中使用强制转换时，我可以将它包装在Objective-C类中。但这绝对不是最舒服的做法。

Answer 1

将您的WindowController.m重命名为WindowController.mm。

如果文件名是.m，整个“翻译单元”将在没有++的ObjC中编译。但是，在test.h中，您要导入包含C ++代码的testlib.h。这些C ++代码在C中无效，从而导致编译器错误。

顺便说一句，

- (id)init {
 testClass = new testlib::Test(0);
 return self;
}

你应该打电话给super的init：

- (id)init {
  if ((self = [super init]))
     testClass = new testlib::Test(0);
  return self;
}

属性

@property void* testClass;

应返回测试*。

@property(readonly,assign) testlib::Test* testClass;

Answer 2

如果您不想重命名该文件，您还可以通过打开文件的“信息”窗口，明确告诉XCode将“.m”文件编译为ObjC ++（单击主文件左侧窗格中的文件名） XCode窗口，然后点击蓝色I“信息”按钮）。将“文件类型”更改为“sourcecode.cpp.objcpp”。

对于示例应用程序，我只是重命名该文件，但如果您有一个不想进行批量重命名的现有代码库，则“文件类型”设置可以很方便。

Answer 3

在“Compile Source As”下将构建设置更改为Objective-c ++，然后点击build

在Objective-C ++中使用C ++类

3 个答案: