This blog is talking about how I install metric_fu in a rails project.

firstly, I typed a command "gem install metric_fu", unfortunatlly, I got a error message like this

"ERROR:  While executing gem ... (Gem::DependencyError)

 Unable to resolve dependencies: metric_fu requires chronic (~> 0.3.0)"

seems that metric_fu can not find the required verion of chronic gem, then I googled chronic, and know that chronic is time parsing tool writen in ruby, the latest version of chronic is 0.6.2. 

so how should I solve this problem?

as I know, a gem package is just like a jar file, which contains  class files and some manifests files. but a gem package can do one more thing - telling you the name and version of those gems it depends on.  so I got a soluation :  change the version declaration of chronic in the "dependency declaration file", telling metric_fu to use the latest verion of chronic.

        Then I  googled again, and a got a import information - people can install gem from source , 

here is the steps:

1. download the correct version of gem source code from  code base (github in general)

        2. build a gem package from the source. 

        3. install the gem package you built.

for more detail, you can see here .

Note : step 2 is the key point.

        before I build my metric_fu gem, I check a file named

        "metric_fu.gemspec", and found out that this is the "dependency description file"

         then I find the dependency description of chronic "s.add_dependency("chronic", [">= 0.3.0"])"

modify the version to "0.6.2", run command "gem build metric_fu.gemspec",  so I got a metric_fu gem depends on chronic 0.6.2.

         finaly, cd to my project directory,

         run command "gem install ../gem_repositry/metric_fu.gem", 

this time, the metric_fu is installed successfully.

         Hope this information is helpful for you.


Update: this is not a good pratice.

                 you can install a old version of chronic manually, and then install metric_fu 2.1.1.

                and I met another problem when running metric_fu in ruby 1.9.2 with syntax 1.0 - "invalid UTF8 charater sequence", you can find the issue here .

                my soluation is just like Jscruggs said . here is my configuration code: do |config| config.syntax_highlighting = false end

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Published on October 02, 2021