背景

在垃圾短信过滤应用 SMSFilters 中,需要使用 Jieba 分词库来対短信进行分词,然后使用 TF-IDF 来进行处理` 分词库是 C++ 写的,这就意味着需要在Swift中集成 C++ 库。
在官方文档 "Using Swift with Cocoa and Objective-C" 中,Apple只是介绍了怎么将 Swift 代码跟 Objective-C 代码做整合,但是没有提C++,后来在官方文档中看到了这样一段话:

You cannot import C++ code directly into Swift. Instead, create an Objective-C or C wrapper for C++ code.

也就是不能直接导入 C++ 代码,但是可以使用 Objective-C 或者 C 对 C++ 进行封装。所以项目中使用 Objective-C 做封装,然后在 Swift 中调用,下面就是这个过程的实践,Demo 代码见 SwiftJiebaDemo

整合过程

分成三步:

  1. 引入C++文件;
  2. 用 Objective-C 封装;
  3. 在 Swift 中 调用 Objective-C;

引入C++文件

Demo中使用的是"结巴"中文分词的 C++ 版本 yanyiwu/cppjieba。将其中的 include/cppjieba 和依赖 limonp 合并,并加入 dict 中的 hmm_modeljiaba.dict 作为基础数据,并暴露 JiebaInitJiebaCut 接口:

//
//  Segmentor.cpp
//  iosjieba
//
//  Created by yanyiwu on 14/12/24.
//  Copyright (c) 2014年 yanyiwu. All rights reserved.
//

#include "Segmentor.h"
#include <iostream>

using namespace cppjieba;

cppjieba::MixSegment * globalSegmentor;

void JiebaInit(const string& dictPath, const string& hmmPath, const string& userDictPath)
{
    if(globalSegmentor == NULL) {
        globalSegmentor = new MixSegment(dictPath, hmmPath, userDictPath);
    }
    cout << __FILE__ << __LINE__ << endl;
}

void JiebaCut(const string& sentence, vector<string>& words)
{
    assert(globalSegmentor);
    globalSegmentor->Cut(sentence, words);
    cout << __FILE__ << __LINE__ << endl;
    cout << words << endl;
}

以及

//
//  Segmentor.h
//  iosjieba
//
//  Created by yanyiwu on 14/12/24.
//  Copyright (c) 2014年 yanyiwu. All rights reserved.
//

#ifndef __iosjieba__Segmentor__
#define __iosjieba__Segmentor__

#include <stdio.h>

#include "cppjieba/MixSegment.hpp"
#include <string>
#include <vector>

extern cppjieba::MixSegment * globalSegmentor;

void JiebaInit(const std::string& dictPath, const std::string& hmmPath, const std::string& userDictPath);

void JiebaCut(const std::string& sentence, std::vector<std::string>& words);

#endif /* defined(__iosjieba__Segmentor__) */

目录如下:

$ tree iosjieba
iosjieba
├── Segmentor.cpp
├── Segmentor.h
├── cppjieba
│   ├── DictTrie.hpp
│   ├── FullSegment.hpp
│   ├── HMMModel.hpp
│   ├── HMMSegment.hpp
│   ├── Jieba.hpp
│   ├── KeywordExtractor.hpp
│   ├── MPSegment.hpp
│   ├── MixSegment.hpp
│   ├── PosTagger.hpp
│   ├── PreFilter.hpp
│   ├── QuerySegment.hpp
│   ├── SegmentBase.hpp
│   ├── SegmentTagged.hpp
│   ├── TextRankExtractor.hpp
│   ├── Trie.hpp
│   ├── Unicode.hpp
│   └── limonp
│       ├── ArgvContext.hpp
│       ├── BlockingQueue.hpp
│       ├── BoundedBlockingQueue.hpp
│       ├── BoundedQueue.hpp
│       ├── Closure.hpp
│       ├── Colors.hpp
│       ├── Condition.hpp
│       ├── Config.hpp
│       ├── FileLock.hpp
│       ├── ForcePublic.hpp
│       ├── LocalVector.hpp
│       ├── Logging.hpp
│       ├── Md5.hpp
│       ├── MutexLock.hpp
│       ├── NonCopyable.hpp
│       ├── StdExtension.hpp
│       ├── StringUtil.hpp
│       ├── Thread.hpp
│       └── ThreadPool.hpp
└── iosjieba.bundle
    └── dict
        ├── hmm_model.utf8
        ├── jieba.dict.small.utf8
        └── user.dict.utf8

接下来开始在项目中集成。首先创建一个空项目 iOSJiebaDemo,将 iosjieba 加入项目中。

单页应用 SwiftJiebaDemo 添加 SwiftJiebaDemo
create-single-view-app swift-jieba-demo-1 swift-jieba-demo-2

添加 iosjieba:

iosjieba-1

见代码: https://github.com/qiwihui/Sw...

C++ 到 Objective-C 封装

这个过程是将 C++ 的接口进行 Objective-C 封装,向 Swift 暴露。这个封装只暴露了 objcJiebaInitobjcJiebaCut 两个接口。

//
//  iosjiebaWrapper.h
//  SMSFilters
//
//  Created by Qiwihui on 1/14/19.
//  Copyright © 2019 qiwihui. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface JiebaWrapper : NSObject

- (void) objcJiebaInit: (NSString *) dictPath forPath: (NSString *) hmmPath forDictPath: (NSString *) userDictPath;
- (void) objcJiebaCut: (NSString *) sentence toWords: (NSMutableArray *) words;

@end
//
//  iosjiebaWrapper.mm
//  iOSJiebaTest
//
//  Created by Qiwihui on 1/14/19.
//  Copyright © 2019 Qiwihui. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "iosjiebaWrapper.h"
#include "Segmentor.h"

@implementation JiebaWrapper

- (void) objcJiebaInit: (NSString *) dictPath forPath: (NSString *) hmmPath forDictPath: (NSString *) userDictPath {

    const char *cDictPath = [dictPath UTF8String];
    const char *cHmmPath = [hmmPath UTF8String];
    const char *cUserDictPath = [userDictPath UTF8String];
    
    JiebaInit(cDictPath, cHmmPath, cUserDictPath);
    
}

- (void) objcJiebaCut: (NSString *) sentence toWords: (NSMutableArray *) words {
    
    const char* cSentence = [sentence UTF8String];
    
    std::vector<std::string> wordsList;
    for (int i = 0; i < [words count];i++)
    {
        wordsList.push_back(wordsList[i]);
    }
    JiebaCut(cSentence, wordsList);
    
    [words removeAllObjects];
    std::for_each(wordsList.begin(), wordsList.end(), [&words](std::string str) {
        id nsstr = [NSString stringWithUTF8String:str.c_str()];
        [words addObject:nsstr];
    });
}

@end

见代码: https://github.com/qiwihui/Sw...

Objective-C 到 Swift

在 Swift 中调用 Objecttive-C 的接口,这个在官方文档和许多博客中都有详细介绍。

  1. 加入 {project_name}-Bridging-Header.h 头文件,即 SwiftJiebaDemo_Bridging_Header_h,引入之前封装的头文件,并在 Targets -> Build Settings -> Objective-C Bridging Header 中设置头文件路径 SwiftJiebaDemo/SwiftJiebaDemo_Bridging_Header_h
//
//  SwiftJiebaDemo-Bridging-Header.h
//  SwiftJiebaDemo
//
//  Created by Qiwihui on 1/15/19.
//  Copyright © 2019 Qiwihui. All rights reserved.
//

#ifndef SwiftJiebaDemo_Bridging_Header_h
#define SwiftJiebaDemo_Bridging_Header_h

#import "iosjiebaWrapper.h"

#endif /* SwiftJiebaDemo_Bridging_Header_h */

bridging-header-2

  1. 将使用到 C++ 的 Objective-C 文件修改为 Objective-C++ 文件,即 将 .m 改为 .mm: iosjiebaWrapper.m 改为 iosjiebaWrapper.mm

见代码:https://github.com/qiwihui/Sw...

使用

使用时需要先初始化 Jiaba分词,然后再进行分词。

class Classifier {

    init() {
        let dictPath = Bundle.main.resourcePath!+"/iosjieba.bundle/dict/jieba.dict.small.utf8"
        let hmmPath = Bundle.main.resourcePath!+"/iosjieba.bundle/dict/hmm_model.utf8"
        let userDictPath = Bundle.main.resourcePath!+"/iosjieba.bundle/dict/user.dict.utf8"

        JiebaWrapper().objcJiebaInit(dictPath, forPath: hmmPath, forDictPath: userDictPath);
    }

    func tokenize(_ message:String) -> [String] {
        print("tokenize...")
        let words = NSMutableArray()
        JiebaWrapper().objcJiebaCut(message, toWords: words)
        return words as! [String]
    }
}

控制台输出结果:

result

可以看到,测试用例 小明硕士毕业于中国科学院计算所,后在日本京都大学深造 经过分词后为
〔拼音〕["小明", "硕士", "毕业", "于", "中国科学院", "计算所", ",", "后", "在", "日本", "京都大学", "深造"],完成集成。

见代码: https://github.com/qiwihui/Sw...

遇到的问题

由于自己对于编译链接原理不了解,以及是 iOS 开发初学,因此上面的这个过程中遇到了很多问题,耗时两周才解决,故将遇到的一些问题记录于此,以便日后。

  1. "cassert" file not found

.m 改为 .mm 即可。

  1. compiler not finding <tr1/unordered_map>

设置 C++ Standard LibraryLLVM libc++

llvm

参考: mac c++ compiler not finding <tr1/unordered_map>

  1. warning: include path for stdlibc++ headers not found; pass '-std=libc++' on the command line to use the libc++ standard library instead [-Wstdlibcxx-not-found]

Build Setting -> C++ Standard Library -> libstdc++ 修改为 Build Setting -> C++ Standard Library -> libc++

  1. use of unresolved identifier

这个问题在于向项目中加入文件时,Target Membership 设置不正确导致。需要将对于使用到的 Target 都勾上。

相关参考: Understanding The "Use of Unresolved Identifier" Error In Xcode

参考

  • SwiftArchitect 对问题 “Can I have Swift, Objective-C, C and C++ files in the same Xcode project?

” 的回答

本文固定链接: http://www.js-code.com/cpp/cpp_61205.html