blocks|key|1401140|text|将你的Gemfile改为使用'mysql2'，它是一个更现代的驱动程序，并且像其他人提到的那样有更好的功能。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1401141|默认情况下，新的Rails应用程序使用mysql2+gem。|1401142|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Change your Gemfile to use 'mysql2', it's a more modern driver and has nicer features as other people have mentioned.

New Rails applications use the mysql2 gem by default.

blocks|key|2279023|text|我遇到了同样的问题(RoR+3，OSX10.6，MySQL2.8.1gem)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2279024|您可以使用irb来排除RoR：|2279025|irb
require+'rubygems'
require+'mysql'
db+=+Mysql.connect('hostname',+'username',+'password',+'database')|code-block|syntax|javascript|2279026|如果上述方法不起作用，您可能想尝试删除mysql+gem并重新安装它。我偶然看到一篇文章，说bundle+install可能会搞砸安装而不会显示错误。|offset|length|style|CODE|2279027|sudo+gem+uninstall+mysql
sudo+env+ARCHFLAGS="-arch+x86_64"+gem+install+mysql+--+--with-mysql-config=/usr/local/mysql/bin/mysql_config|2279028|通过irb验证是否正常工作，然后再次启动rails。|2279029|entityMap^0|0|0|0|1A|E|0|0|2|3|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@$K|Y|L|Z|M|N]]|9|@]|A|$]]|$1|O|3|P|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|11|8|@$K|12|L|13|M|N]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

I ran into the same issue (RoR 3, OSX 10.6, mysql 2.8.1 gem). 

You can use irb to rule out RoR:

<pre><code>irb
require 'rubygems'
require 'mysql'
db = Mysql.connect('hostname', 'username', 'password', 'database')
</code></pre>

If the above doesn't work, you may want to try removing the mysql gem and reinstalling it. I came across a post saying <code>bundle install</code> might mess up the install without displaying errors. 

<pre><code>sudo gem uninstall mysql
sudo env ARCHFLAGS="-arch x86_64" gem install mysql -- --with-mysql-config=/usr/local/mysql/bin/mysql_config
</code></pre>

Verify things work via <code>irb</code>, then start up rails again.

blocks|key|657977|text|我最终从mysql+gem切换到ruby-mysql+gem，成功了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|657978|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I ended up switching from the mysql gem to the ruby-mysql gem, worked.

blocks|key|2278959|text|对于典型的简单用法(连接、查询、迭代结果)，我发现了mysql2+gem，它比mysql或ruby-mysql+gem快得多，并且可以将值自动转换为正确的类型。它可以完美地安装在雪豹上，而我不能让mysql+gem工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2278960|欲了解更多信息，请访问http://github.com/brianmario/mysql2|offset|length|2278961|entityMap|0|LINK|mutability|MUTABLE|url|http://github.com/brianmario/mysql2^0|0|B|Z|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

For simple usage, which is typical (connecting, querying, iterating over results), I found mysql2 gem which is much faster than mysql or ruby-mysql gems and auto-casts values to proper types. And it installes perfectly on Snow Leopard while I couldn't get mysql gem to work.

More info at <a href="http://github.com/brianmario/mysql2" rel="nofollow">http://github.com/brianmario/mysql2</a>

blocks|key|1401074|text|我想我已经找到解决这个问题的办法了。在我的例子中，问题是mysql+gem没有使用bundler正确安装。当我这样做的时候：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1401075|捆绑包安装mysql+(没有意义的错误)|1401076|所有gem都放到了mysql目录下，但后来我检查了bundler+gem的文档，并这样做了：|1401077|bundle+install+bundler_files+(了解gem在未来的位置)|1401078|一切看起来都很正常，除了在安装mysql+gem时我遇到了一些错误。我注意到这是因为我的文件夹路径"/home/pawel/Aptana+Studio+Workspace/myrails_app“|1401079|如果您的文件夹路径中有空格，此gem将无法正确安装，稍后当您将路径修改为没有空格的路径并尝试安装mysql+gem时，它不会显示任何错误，但安装将被破坏，因为您将有一些额外的文件夹与一些文件等|1401080|使用以下命令删除由创建的GEM文件夹并重新安装GEM：|offset|length|style|BOLD|1401081|捆绑包安装|1401082|这就解决了问题。|1401083|entityMap^0|0|0|0|0|0|0|9|I|0|0|5|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Z|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|10|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|11|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|12|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|13|8|@$N|14|O|15|P|Q]]|9|@]|A|$]]|$1|R|3|S|5|6|7|16|8|@$N|17|O|18|P|Q]]|9|@]|A|$]]|$1|T|3|U|5|6|7|19|8|@]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|W|$]]

I think I have found the solution for the problem. In my case the problem was that the mysql gem hasn't been properly installed using the bundler . when I did this:

bundle install mysql (noobish mistake)

all gems went to mysql directory, but later on I have checked the docs of the bundler gem
and did this:

bundle install bundler_files ( to know where the gems are in the future)

everything looked almost ok except that when mysql gem was installing i got some errors.
I noticed that it was because of my folder path "/home/pawel/Aptana Studio Workspace/myrails_app"

If you have spaces in your folder path this gem wont install properly and later on when you modify the path to one without spaces and try to install the mysql gem IT WONT DISPLAY ANY ERRORS, but the installation will be corrupted, because you will have some extra folders there with some files etc. so 

DELETE THE GEM FOLDER CREATED BY BUNDLER AND REINSTALL GEMS WITH THIS COMMAND:

bundle install

That solved the problem.

blocks|key|1401125|text|您可以尝试切换到mysql2+gem，它将为您解决所有这些问题。请参阅：https://github.com/brianmario/mysql2/|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1401126|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/brianmario/mysql2/^0|10|11|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

you can try switching to the mysql2 gem which should resolve all that issues for you. see: <a href="https://github.com/brianmario/mysql2/" rel="nofollow">https://github.com/brianmario/mysql2/</a>

blocks|key|3686571|text|我认为发生的情况是mysql+gem无法加载mysql动态库(应该由本机MySQL安装提供)。要测试这种情况是否正在发生，请执行以下操作|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3686572|$+irb
1.9.2p320+:001+>+require+'mysql_api'
+=>+true+
1.9.2p320+:002+>+|code-block|syntax|javascript|3686573|如果它不能加载这个低级的mysql_api+(它实际上为mysql+gem提供了功能)，它会给你一些潜在的有用的错误。通常它找不到动态库。为了解决这个问题，我找到了几个解决方案：|offset|length|style|CODE|3686574|在http://wonko.com/post/how-to-install-the-mysqlruby-gem-on-mac-os-x-leopard中，执行以下操作|3686575|适用于系统范围的安装|3686576|sudo+env+ARCHFLAGS="-arch+i386"+gem+install+mysql+--+\
++--with-mysql-dir=/usr/local/mysql+--with-mysql-lib=/usr/local/mysql/lib+\
++--with-mysql-include=/usr/local/mysql/include|3686577|或本地安装|3686578|env+ARCHFLAGS="-arch+i386"+gem+install+mysql+--+\
++--with-mysql-dir=/usr/local/mysql+--with-mysql-lib=/usr/local/mysql/lib+\
++--with-mysql-include=/usr/local/mysql/include|3686579|然后从http://alexbraunstein.com/2011/08/12/library-loaded-libmysqlclient-18-dylib/放入.bash_profile|3686580|export+DYLD_LIBRARY_PATH=/usr/local/mysql/lib:$DYLD_LIBRARY_PATH+|3686581|entityMap|0|LINK|mutability|MUTABLE|url|http://wonko.com/post/how-to-install-the-mysqlruby-gem-on-mac-os-x-leopard|1|http://alexbraunstein.com/2011/08/12/library-loaded-libmysqlclient-18-dylib/^0|0|0|C|9|S|5|0|1|22|0|0|0|0|0|0|29|D|3|24|1|0|0^^$0|@$1|2|3|4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1C|8|@$I|1D|J|1E|K|L]|$I|1F|J|1G|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|1H|8|@]|9|@$I|1I|J|1J|1|1K]]|A|$]]|$1|O|3|P|5|6|7|1L|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|1M|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1N|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|1O|8|@]|9|@]|A|$E|F]]|$1|W|3|X|5|6|7|1P|8|@$I|1Q|J|1R|K|L]]|9|@$I|1S|J|1T|1|1U]]|A|$]]|$1|Y|3|Z|5|D|7|1V|8|@]|9|@]|A|$E|F]]|$1|10|3|-4|5|6|7|1W|8|@]|9|@]|A|$]]]|11|$12|$5|13|14|15|A|$16|17]]|18|$5|13|14|15|A|$16|19]]]]

I think what happens is that the mysql gem isn't able to load the mysql dynamic library (supposed to be supplied by the native MySQL installation). To test whether this is happening, do this

<pre><code>$ irb
1.9.2p320 :001 &gt; require 'mysql_api'
 =&gt; true 
1.9.2p320 :002 &gt; 
</code></pre>

If it isn't able to load this low level <code>mysql_api</code>, (which actually supplies the functionality to the <code>mysql</code> gem), it will give you some potentially useful errors. Usually it is not able to find the dynamic library. To remedy this, I found a couple of solutions: 

From <a href="http://wonko.com/post/how-to-install-the-mysqlruby-gem-on-mac-os-x-leopard" rel="nofollow">http://wonko.com/post/how-to-install-the-mysqlruby-gem-on-mac-os-x-leopard</a>, do this

For system-wide install

<pre><code>sudo env ARCHFLAGS="-arch i386" gem install mysql -- \
 --with-mysql-dir=/usr/local/mysql --with-mysql-lib=/usr/local/mysql/lib \
 --with-mysql-include=/usr/local/mysql/include
</code></pre>

or local install

<pre><code>env ARCHFLAGS="-arch i386" gem install mysql -- \
 --with-mysql-dir=/usr/local/mysql --with-mysql-lib=/usr/local/mysql/lib \
 --with-mysql-include=/usr/local/mysql/include
</code></pre>

and then from <a href="http://alexbraunstein.com/2011/08/12/library-loaded-libmysqlclient-18-dylib/" rel="nofollow">http://alexbraunstein.com/2011/08/12/library-loaded-libmysqlclient-18-dylib/</a> put in <code>.bash_profile</code>:

<pre><code>export DYLD_LIBRARY_PATH=/usr/local/mysql/lib:$DYLD_LIBRARY_PATH 
</code></pre>

blocks|key|1405171|text|在升级到Snow+Leopard后，我也遇到了同样的问题。在安装MySQL+gem时，我收到了一堆关于文档的错误，然后，在运行服务器时：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1405172|undefined+method+`init'+for+Mysql:Class|code-block|syntax|javascript|1405173|我在其他gem中也遇到了一些类似但不相关的问题，特别是那些具有需要编译的C组件的gem，比如RedCloth和hpricot：|1405174|Unable+to+compile+native+extensions|1405175|这些错误与base64架构中的本机扩展有关。解决方案有三个方面：|1405176|1405177|我重新安装了XCode+4。升级到雪豹已经破坏了我的C编译器，所以一些gem无法编译。这让我更近了一步，但并没有解决这个问题。|ordered-list-item|1405178|I失败了，并重新安装了RVM。它似乎是在一个目录中安装gem，然后在另一个目录中找到它们。这修复了每个本机架构的base64错误，但MySQL+gem仍然失败。|1405179|I移除并将MySQL降级到版本5.1。这修复了MySQL+gem问题。|1405180|1405181|现在一切又好起来了。|1405182|entityMap^0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|11|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|13|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|14|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|15|8|@]|9|@]|A|$]]|$1|Q|3|R|5|P|7|16|8|@]|9|@]|A|$]]|$1|S|3|T|5|P|7|17|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|18|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|19|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|Y|$]]

I has the same issue after upgrading to Snow Leopard. On installing the MySQL gem, I got a bunch of errors about the documentation, then, on running the server:

<pre><code>undefined method `init' for Mysql:Class
</code></pre>

I was also having some similar, but unrelated issues with other gems, particularly those that had C components that needed compiling such as RedCloth and hpricot:

<pre><code>Unable to compile native extensions
</code></pre>

These errors were to do with native extensions in base 64 architecture. The solution was threefold:

<ol>
<li>I reinstalled XCode 4. The upgrade to Snow Leopard had broken my C compiler, so some gems were failing to compile. This took me a step closer, but didn't fix the issue.</li>
<li>I blew away and reinstalled RVM. It appeared to be installing gems in one directory, and finding them in another. This fixed every native architecture base64 error, but the MySQL gem was still failing.</li>
<li>I removed and downgraded MySQL to version 5.1. This fixed the MySQL gem issue.</li>
</ol>

All is now well again.

Trying to start a new Rails 3 beta 4 app with mysql.... Running OS X Snow Leopard. WIth previous versions of Rails I have no problem with MySQL. But now when I start the Rails 3 app I get the following error when I click "About Your Application Environment" on the Rails index.html startup screen:

undefined method `init' for Mysql:Class

Rails 3 Mysql Problems

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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正在尝试使用mysql启动一个新的Rails 3 beta 4应用程序...运行OS X雪豹。对于以前版本的Rails，我使用MySQL没有任何问题。但是现在，当我启动Rails 3应用程序时，当我在Rails index.html启动屏幕上点击“关于你的应用程序环境”时，我得到了以下错误：Mysql的未定义方法‘`init’：Class

问Rails 3 Mysql问题
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回答 8

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