vim 自动补全youcompleteme怎么选择

YouCompleteMe的特别之处
基于语义补全
总所周知，Vim是一款文本编辑器。也就是说，其最基础的工作就是编辑文本，而不管该文本的内容是什么。在Vim被程序员所使用后，其慢慢的被肩负了与IDE一样的工作，文本自动补全(ie.acp,omnicppcompleter)，代码检查(Syntastic)等等工作。
针对文本自动补全这个功能来说，主要有两种实现方式。
基于文本
我们常用的omnicppcompleter,acp,vim自带的c-x, c-n的实现方式就是基于文本。更通俗的说法，其实就是一个字：
猜
其通过文本进行一些正则表达式的匹配，再根据生成的tags(利用ctags生成)来实现自动补全的效果。
基于语义
顾名思义，其是通过分析源文件，经过语法分析以后进行补全。由于对源文件进行分析，基于语义的补全可以做到很精确。但是这显然是vim所不可能支持的。而且经过这么多年发展，由于语法分析有很高的难度，也一直没有合适的工具出现。直到，由apple支持的clang/llvm横空出世。YouCompleteMe也正是在clang/llvm的基础上进行构建的。
整合实现了多种插件
clang_complete
AutoComplPop
Supertab
neocomplcache
Syntastic(类似功能,仅仅针对c/c++/obj-c代码)
支持语言
c
c++
obj-c
c#
python
对于其他的语言，会调用vim设置的omnifunc来匹配，因此同样支持php,ruby等语言。
已知的有 * javascript —-tern_for_vim * ruby/java —-eclim
使用效果图

使用感受
和IDE一样，自动补全，
根据include的文件进行补全
不用再蹩脚的生成tags
补全非常精准，而且速度很快，不会有延迟(以前在大项目上，acp用起来实在是很卡)
支持类似tags的跳转，跳到定义处以及使用处
出错提示很智能，并且用起来真的是如丝般柔滑，不用输入:w进行强制检测
安装
说完了那么多好处，就要说到安装了。不同于以往其他vim插件，YCM是一款编译型的插件。在下载完后，需要手动编译后才能使用。对应其他的插件来说，仅仅就是把.vim的文件丢到相应文件夹下就可以。而这也加大了使用YCM的难度。
安装准备
最新版的Vim(7.3.584+)，编译时添加+python标志(已经安装的可以通过vim --version查看)
cmake(mac可以通过homebrew安装，brew install cmake,ubuntu可以通过sudo apt-get install cmake)
安装vundle插件，用于安装管理vim的插件
mac下快速安装
在.vimrc中添加下列代码
Bundle 'Valloric/YouCompleteMe'

保存退出后打开vim，在正常模式下输入
:BundleInstall

等待vundle将YouCompleteMe安装完成
而后进行编译安装：
cd ~/.vim/bundle/YouCompleteMe
./install --clang-completer

如果不需要c-family的补全，可以去掉--clang-completer。如果需要c#的补全，请加上--omnisharp-completer。
正常来说,YCM会去下载clang的包，如果已经有，也可以用系统--system-libclang。
就这样，安装结束。打开vim，如果没有提示YCM未编译，则说明安装已经成功了。
手动编译安装
安装的脚本并不是什么时候都好用，至少对我来说是这样的。安装完之后出现了问题，参考issue#809。
在用:BundleInstall安装完成或者使用
git clone --recursive https://github.com/Valloric/YouCompleteMe.git

获取最新的仓库，而后使用git submodule update --init --recursive确认仓库的完整性后，开始安装流程。
下载最新的clang二进制文件 YCM要求clang版本 > 3.2，一般来说都是下载最新的。
安装python-dev.(ubuntu下使用sudo apt-get install python-dev,mac下默认提供，否则请安装command line tools)
编译
cd ~
mkdir ycm_build
cd ycm_build
cmake -G “Unix Makefiles” -DPATH_TO_LLVM_ROOT=~/ycm_temp/llvm_root_dir . ~/.vim/bundle/YouCompleteMe/cpp make ycm_support_libs

这里需要注意的是，~/ycm_temp/llvm_root_dir中包含的是根据第一步下载的压缩包解压出来的内容(包括include, bin等等文件)。
这样就完成了,开始感受YCM提供的完全不逊色于大型IDE所提供的自动补全功能吧。
配置
不同于很多vim插件，YCM首先需要编译，另外还需要有配置。在vim启动后，YCM会找寻当前路径以及上层路径的.ycm_extra_conf.py.在~/.vim/bundle/YouCompleteMe/cpp/ycm/.ycm_extra_conf.py中提供了默认的模板。也可以参考我的(就在模板上改改而已)。不过这个解决了标准库提示找不到的问题。
一般来说,我会在~目录下放一个默认的模板，而后再根据不同的项目在当前目录下再拷贝个.ycm_extra_conf.py。
# This file is NOT licensed under the GPLv3, which is the license for the rest
# of YouCompleteMe.
#
# Here's the license text for this file:
#
# This is free and unencumbered software released into the public domain.
#
# Anyone is free to copy, modify, publish, use, compile, sell, or
# distribute this software, either in source code form or as a compiled
# binary, for any purpose, commercial or non-commercial, and by any
# means.
#
# In jurisdictions that recognize copyright laws, the author or authors
# of this software dedicate any and all copyright interest in the
# software to the public domain. We make this dedication for the benefit
# of the public at large and to the detriment of our heirs and
# successors. We intend this dedication to be an overt act of
# relinquishment in perpetuity of all present and future rights to this
# software under copyright law.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.
#
# For more information, please refer to

import os
import ycm_core

# These are the compilation flags that will be used in case there's no
# compilation database set (by default, one is not set).
# CHANGE THIS LIST OF FLAGS. YES, THIS IS THE DROID YOU HAVE BEEN LOOKING FOR.
flags = [
'-Wall',
'-Wextra',
#'-Werror',
#'-Wc++98-compat',
'-Wno-long-long',
'-Wno-variadic-macros',
'-fexceptions',
'-stdlib=libc++',
# THIS IS IMPORTANT! Without a "-std=" flag, clang won't know which
# language to use when compiling headers. So it will guess. Badly. So C++
# headers will be compiled as C headers. You don't want that so ALWAYS specify
# a "-std=".
# For a C project, you would set this to something like 'c99' instead of
# 'c++11'.
'-std=c++11',
# ...and the same thing goes for the magic -x option which specifies the
# language that the files to be compiled are written in. This is mostly
# relevant for c++ headers.
# For a C project, you would set this to 'c' instead of 'c++'.
'-x',
'c++',
'-I',
'.',
'-isystem',
'/usr/include',
'-isystem',
'/usr/local/include',
'-isystem',
'/Library/Developer/CommandLineTools/usr/include',
'-isystem',
'/Library/Developer/CommandLineTools/usr/bin/../lib/c++/v1',
]

# Set this to the absolute path to the folder (NOT the file!) containing the
# compile_commands.json file to use that instead of 'flags'. See here for
# more details: http://clang.llvm.org/docs/JSONCompilationDatabase.html
#
# Most projects will NOT need to set this to anything; you can just change the
# 'flags' list of compilation flags. Notice that YCM itself uses that approach.
compilation_database_folder = ''

if os.path.exists( compilation_database_folder ):
database = ycm_core.CompilationDatabase( compilation_database_folder )
else:
database = None

SOURCE_EXTENSIONS = [ '.cpp', '.cxx', '.cc', '.c', '.m', '.mm' ]

def DirectoryOfThisScript():
return os.path.dirname( os.path.abspath( __file__ ) )

def MakeRelativePathsInFlagsAbsolute( flags, working_directory ):
if not working_directory:
return list( flags )
new_flags = []
make_next_absolute = False
path_flags = [ '-isystem', '-I', '-iquote', '--sysroot=' ]
for flag in flags:
new_flag = flag

if make_next_absolute:
make_next_absolute = False
if not flag.startswith( '/' ):
new_flag = os.path.join( working_directory, flag )

for path_flag in path_flags:
if flag == path_flag:
make_next_absolute = True
break

if flag.startswith( path_flag ):
path = flag[ len( path_flag ): ]
new_flag = path_flag + os.path.join( working_directory, path )
break

if new_flag:
new_flags.append( new_flag )
return new_flags

def IsHeaderFile( filename ):
extension = os.path.splitext( filename )[ 1 ]
return extension in [ '.h', '.hxx', '.hpp', '.hh' ]

def GetCompilationInfoForFile( filename ):
# The compilation_commands.json file generated by CMake does not have entries
# for header files. So we do our best by asking the db for flags for a
# corresponding source file, if any. If one exists, the flags for that file
# should be good enough.
if IsHeaderFile( filename ):
basename = os.path.splitext( filename )[ 0 ]
for extension in SOURCE_EXTENSIONS:
replacement_file = basename + extension
if os.path.exists( replacement_file ):
compilation_info = database.GetCompilationInfoForFile(
replacement_file )
if compilation_info.compiler_flags_:
return compilation_info
return None
return database.GetCompilationInfoForFile( filename )

def FlagsForFile( filename, **kwargs ):
if database:
# Bear in mind that compilation_info.compiler_flags_ does NOT return a
# python list, but a "list-like" StringVec object
compilation_info = GetCompilationInfoForFile( filename )
if not compilation_info:
return None

final_flags = MakeRelativePathsInFlagsAbsolute(
compilation_info.compiler_flags_,
compilation_info.compiler_working_dir_ )

# NOTE: This is just for YouCompleteMe; it's highly likely that your project
# does NOT need to remove the stdlib flag. DO NOT USE THIS IN YOUR
# ycm_extra_conf IF YOU'RE NOT 100% SURE YOU NEED IT.
#try:
# final_flags.remove( '-stdlib=libc++' )
#except ValueError:
# pass
else:
relative_to = DirectoryOfThisScript()
final_flags = MakeRelativePathsInFlagsAbsolute( flags, relative_to )

return {
'flags': final_flags,
'do_cache': True
}

YouCompleteMe提供的其他功能
YCM除了提供了基本的补全功能,自动提示错误的功能外,还提供了类似tags的功能：
跳转到定义GoToDefinition
跳转到声明GoToDeclaration
以及两者的合体GoToDefinitionElseDeclaration
可以在.vimrc中配置相应的快捷键。

nnoremap gl :YcmCompleter GoToDeclaration

nnoremap gf :YcmCompleter GoToDefinition
nnoremap gg :YcmCompleter GoToDefinitionElseDeclaration

另外，YCM也提供了丰富的配置选项，同样在.vimrc中配置。具体请参考

let g:ycm_error_symbol = '>>'

let g:ycm_warning_symbol = '>*'

同时，YCM可以打开location-list来显示警告和错误的信息:YcmDiags。个人关于ycm的配置如下：
" for ycm
let g:ycm_error_symbol = '>>'
let g:ycm_warning_symbol = '>*'
nnoremap gl :YcmCompleter GoToDeclaration
nnoremap gf :YcmCompleter GoToDefinition
nnoremap gg :YcmCompleter GoToDefinitionElseDeclaration
nmap :YcmDiags

YCM提供的跳跃功能采用了vim的jumplist，往前跳和往后跳的快捷键为Ctrl+O以及Ctrl+I。
总结
YouCompleteMe是我用过的最爽的一个自动补全的插件了。之前使用acp时，遇到大文件基本上就卡死了，以至于都不怎么敢使用。由于YCM使用的时C/S结构，部分使用vim脚本编写，部分认为原生代码，使得跑起来速度飞快。