How do I reference functions in other files with leiningen?

Question

I'm still fairly new to Clojure so I apologize if this is a completely newbie question but I wasn't able to find a sufficient answer online. Basically, my problem is that any time I try to run my project, I get an error like: ``` Exception in thread "main" java.lang.RuntimeException: java.io.FileNotFoundException: Could not locate greeter__init.class or greeter.clj on classpath: ``` In this case, greeter.clj is in the project in the same directory as the file containing my main function. For illustration purposes, I've created a project that has a directory tree like this: My code for core.clj is as follows: ``` (ns omg.core (require [greeter])) (defn -main[] (greet)) ``` My code for greeter.clj is: ``` (ns greeter) (defn greet [] println("Hello world")) ``` Whenever I type `lein run -m omg.core` I get the exception mentioned above. What am I doing wrong?

Accepted Answer

the greeter namespace it at the wrong level

```
(ns omg.greeter)
```

The names in namespace correspond to the folders in the path so to use the file in /src/omg/greeter.clj that file should contain the `omg.greeter` namespace. if you want to have it just called `greeter` then move it down one folder

When using `require` you need to spell out the namespace of the function you are calling, in this case that would be `(omg.greeter/greet)`. since this is a pain, the `use` function requires a namespace and adds all it's functions to the current namespace. Another option that is more selective is to use require with a :refer option in the namespace definition

```
(ns omg.core
    (require [omg.greeter :refer :all]))
```

or

```
(ns omg.core
    (require [omg.greeter :refer [greet]]))
```

Most people put the namespace requirements into the `ns` call at the top of the file.

a quick read of http://clojure.org/namespaces will hopefully help

How do I reference functions in other files with leiningen?

Solution

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