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A simple Webpage

Hello World is a good start, but what if you want something a bit more fancy.. Something like an HTML document saying "Hello World". If that's what you want, follow along:

Basic Webpage

Let's start our webpage with.. well.. a webpage. But before we create a webpage we need to place it somewhere Crow recognizes, for now this directory is going to be called templates, but we can change it later.

Once our templates folder is created, we can create our HTML document inside it, let's call it fancypage.html.

After that we can just place something simple inside it like:

templates/fancypage.html
<!DOCTYPE html>
<html>
  <body>
  <p>Hello World!</p>
  </body>
</html>

Now that we have our HTML page ready, let's take our Hello World example from earlier:
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#include "crow.h"
//#include "crow_all.h"

int main()
{
    crow::SimpleApp app; //define your crow application

    //define your endpoint at the root directory
    CROW_ROUTE(app, "/")([](){
        return "Hello world";
    });

    //set the port, set the app to run on multiple threads, and run the app
    app.port(18080).multithreaded().run();
}

And now let's modify it so that it returns our cool page:

/main.cpp
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#include "crow.h"
//#include "crow_all.h"

int main()
{
    crow::SimpleApp app;

    //define your endpoint at the root directory
    CROW_ROUTE(app, "/")([](){
        auto page = crow::mustache::load_text("fancypage.html");
        return page;
    });

    app.port(18080).multithreaded().run();
}

Your project should look something something like:

./
 |-templates/
 |          |-fancypage.html
 |
 |-main.cpp
 |-crow_all.h
or
./
 |-templates/
 |          |-fancypage.html
 |
 |-crow/
 |     |-include/...
 |     |-crow.h
 |-main.cpp

Once the code is done compiling, if we call http://localhost:18080/ we get our Hello World in an HTML document rather than just plain text.

Note

Compilation instructions are available for Linux, MacOS, and Windows

Template Webpage with a variable

But we can make things even more exciting, we can greet a user by their name instead!!

Let's start with our webpage, and modify it with a little bit of mustache syntax:

templates/fancypage.html
<!DOCTYPE html>
<html>
  <body>
  <p>Hello {{person}}!</p> <!--(1)-->
  </body>
</html>

  1. {{}} in mustache define a simple variable


Now let's modify our C++ code to use the variable we just added to our webpage (or template):

/main.cpp
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#include "crow.h"
//#include "crow_all.h"

int main()
{
    crow::SimpleApp app;

    //define your endpoint at the root directory
    CROW_ROUTE(app, "/<string>")([](std::string name){ // (1)
        auto page = crow::mustache::load("fancypage.html"); // (2)
        crow::mustache::context ctx ({{"person", name}}); // (3)
        return page.render(ctx); //(4)
    });

    app.port(18080).multithreaded().run();
}

  1. We are adding a string variable to the URL and a counterpart (std::string name) to our Route, this can be anything the user wants.
  2. We are using load() instead of load_text() since we have an actual variable now.
  3. We are creating a new context containing the person variable from our template and the name we got from the URL.
  4. we are using render(ctx) to apply our context to the template.

Now (after compiling the code and running the executable a second time) calling http://localhost:18080/Bob should return a webpage containing "Hello Bob!". We did it!

For more details on templates and HTML pages in Crow please go here