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Diffstat (limited to '_content/doc/tutorial/call-module-code.html')
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1 files changed, 114 insertions, 110 deletions
diff --git a/_content/doc/tutorial/call-module-code.html b/_content/doc/tutorial/call-module-code.html index 3c3602b8..bce43d72 100644 --- a/_content/doc/tutorial/call-module-code.html +++ b/_content/doc/tutorial/call-module-code.html @@ -4,7 +4,7 @@ }--> <p> - In the <a href="create-module.html">previous section</a>, you created a + In the <a href="/doc/tutorial/create-module.html">previous section</a>, you created a <code>greetings</code> module. In this section, you'll write code to make calls to the <code>Hello</code> function in the module you just wrote. You'll write code you can execute as an application, and which calls code in the @@ -13,7 +13,7 @@ <aside class="Note"> <strong>Note:</strong> This topic is part of a multi-part tutorial that begins - with <a href="create-module.html">Create a Go module</a>. + with <a href="/doc/tutorial/create-module.html">Create a Go module</a>. </aside> <ol> @@ -22,8 +22,16 @@ is where you'll write your caller. <p> - For example, if your current directory in the command prompt is the - greetings directory, you could use the following commands: + After you create this directory, you should have both a hello and a + greetings directory at the same level in the hierarchy, like so: + </p> + <pre><home>/ + |-- greetings/ + |-- hello/</pre> + + <p> + For example, if your command prompt is in the greetings directory, you + could use the following commands: </p> <pre> @@ -35,7 +43,28 @@ cd hello </li> <li> - In your text editor (in the hello directory), create a file in which to + Enable dependency tracking for the code you're about to write. + + <p> + To enable dependency tracking for your code, run the + <a + href="/ref/mod#go-mod-init" + ><code>go mod init</code> command</a>, giving it the name of the module + your code will be in.</p> + + <p> + For the purposes of this tutorial, use <code>example.com/hello</code> + for the module path. + </p> + + <pre> +$ go mod init example.com/hello +go: creating new go.mod: module example.com/hello +</pre> + </li> + + <li> + In your text editor, in the hello directory, create a file in which to write your code and call it hello.go. </li> @@ -61,8 +90,7 @@ func main() { message := greetings.Hello("Gladys") fmt.Println(message) } -</pre - > +</pre> <p> In this code, you: @@ -71,16 +99,16 @@ func main() { <ul> <li> Declare a <code>main</code> package. In Go, code executed as an - application must go in a <code>main</code> package. + application must be in a <code>main</code> package. </li> <li> Import two packages: <code>example.com/greetings</code> and - <code>fmt</code>. This gives your code access to functions in those - packages. Importing <code>example.com/greetings</code> (the package - contained in the module you created earlier) gives you access to the - <code>Hello</code> function. You also import <code>fmt</code>, with - functions for handling input and output text (such as printing text to - the console). + the <a href="https://pkg.go.dev/fmt/"><code>fmt</code> package</a>. This + gives your code access to functions in those packages. Importing + <code>example.com/greetings</code> (the package contained in the module + you created earlier) gives you access to the <code>Hello</code> + function. You also import <code>fmt</code>, with functions for handling + input and output text (such as printing text to the console). </li> <li> Get a greeting by calling the <code>greetings</code> package’s @@ -90,148 +118,124 @@ func main() { </li> <li> - Create a new module for this hello package. + Edit the <code>example.com/hello</code> module to use your local + <code>example.com/greetings</code> module. <p> - From the command line at the hello directory, run the - <code>go mod init</code> command, giving it the name of the module your - code will be in (here, just use "hello"). - </p> - - <pre> -$ go mod init hello -go: creating new go.mod: module hello -</pre - > - </li> - - <li> - Edit the <code>hello</code> module to use the unpublished greetings module. - - <p> - For production use, you’d publish your modules on a server, either inside - your company or on the internet, and the Go command will download them - from there. For now, you need to adapt the caller's module so it can find - the greetings code on your local file system. + For production use, you’d publish the <code>example.com/greetings</code> + module from its repository (with a module path that reflected its published + location), where Go tools could find it to download it. + For now, because you haven't published the module yet, you need to adapt + the <code>example.com/hello</code> module so it can find the + <code>example.com/greetings</code> code on your local file system. </p> <p> - To do that, make a small change to <code>hello</code> module’s go.mod - file. + To do that, use the + <a href="/ref/mod#go-mod-edit"><code>go + mod edit</code> command</a> to edit the <code>example.com/hello</code> + module to redirect Go tools from its module path (where the module isn't) + to the local directory (where it is). </p> <ol> <li> - In the hello directory, open the go.mod file, change it so that it looks - like the following, and save the file. + From the command prompt in the hello directory, run the following + command: + + <pre> +$ go mod edit -replace=example.com/greetings=../greetings +</pre> + + <p> + The command specifies that <code>example.com/greetings</code> should be + replaced with <code>../greetings</code> for the purpose of locating the + dependency. After you run the command, the go.mod file in the hello + directory should include a <a href="/doc/modules/gomod-ref#replace"> + <code>replace</code> directive</a>: + </p> <pre> -module hello +module example.com/hello -go 1.14 +go 1.16 <ins>replace example.com/greetings => ../greetings</ins> </pre> - - <p> - Here, the - <a href="/ref/mod#go-mod-file-replace"> - <code>replace</code> directive - </a> - tells Go to replace the module path (the URL - <code>example.com/greetings</code>) with a path you specify. In this - case, that's a greetings directory next to the hello directory. - </p> </li> <li> - In the hello directory, run <code>go build</code> to make Go locate the - module and add it as a dependency to the go.mod file. + From the command prompt in the hello directory, run the + <a href="/ref/mod#go-mod-tidy"> + <code>go mod tidy</code> command</a> to synchronize the + <code>example.com/hello</code> module's dependencies, adding those + required by the code, but not yet tracked in the module. - <pre> -$ go build + <pre>$ go mod tidy go: found example.com/greetings in example.com/greetings v0.0.0-00010101000000-000000000000 -</pre - > - </li> - - <li> - Look at go.mod again to see the changes made by <code>go build</code>, - including the <code>require</code> directive Go added. +</pre> + <p> + After the command completes, the <code>example.com/hello</code> + module's go.mod file should look like this: + </p> - <pre> -module hello + <pre>module example.com/hello -go 1.14 +go 1.16 replace example.com/greetings => ../greetings -<ins>require example.com/greetings v0.0.0-00010101000000-000000000000</ins> -</pre> +<ins>require example.com/greetings v0.0.0-00010101000000-000000000000</ins></pre> <p> - To build the module, Go found the local code in the ../greetings - directory, then added a - <a href="/ref/mod#go-mod-file-require"> - <code>require</code> directive - </a> - to specify that <code>hello</code> is dependent on (requires) - <code>example.com/greetings</code>. You created this dependency when - you imported the <code>greetings</code> package (contained in the - greetings module) in hello.go. The <code>replace</code> directive - tells Go where to find the <code>greetings</code> module, because it - isn't published yet. + The command found the local code in the greetings directory, then + added a <a href="/doc/modules/gomod-ref#require"><code>require</code> + directive</a> to specify that <code>example.com/hello</code> + requires <code>example.com/greetings</code>. You created this + dependency when you imported the <code>greetings</code> package in + hello.go. + </p> + <p> + The number following the module path is a <em>pseudo-version number</em> + -- a generated number used in place of a semantic version number (which + the module doesn't have yet). </p> - <p> - To reference a published module, a go.mod file would omit the - <code>replace</code> directive and use a - <code>require</code> directive with a tagged version number at the - end. + To reference a <em>published</em> module, a go.mod file would + typically omit the <code>replace</code> directive and use a + <code>require</code> directive with a tagged version number at the end. </p> <pre>require example.com/greetings v1.1.0</pre> + + <p>For more on version numbers, see + <a href="/doc/modules/version-numbers">Module version numbering</a>.</p> </li> </ol> - </li> - <li> - In the <code>hello</code> directory, run the <code>hello</code> executable - (created by <code>go build</code>) to confirm that the code works. - <ul> - <li> - On Linux or Mac: + At the command prompt in the <code>hello</code> directory, run your code to + confirm that it works. - <pre> -$ ./hello -Hi, Gladys. Welcome! -</pre - > - </li> - - <li> - On Windows: - - <pre> -$ hello.exe + <pre> +$ go run . Hi, Gladys. Welcome! -</pre - > - </li> - </ul> +</pre> </li> </ol> <p> - Congrats! You've written two functioning modules. In the tutorial's - <a href="handle-errors.html">next topic</a>, you'll add some error handling. + Congrats! You've written two functioning modules. +</p> + +<p> + In the next topic, you'll add some error handling. </p> <p class="Navigation"> - <a class="Navigation-prev" href="create-module.html" + <a class="Navigation-prev" href="/doc/tutorial/create-module.html" >< Create a Go module</a > - <a class="Navigation-next" href="handle-errors.html" + <a class="Navigation-next" href="/doc/tutorial/handle-errors.html" >Return and handle an error ></a > </p> |