C++ string template library

Question

I want simple C++ string based template library to replace strings at runtime.

For example, I will use

string template = \"My name is {{name}}\";


        

Answer 1

Have you considered a set of inline functions that use ostringstram instead of "string templates"?

inline std::string name_template(const std::string& name)
{
    std::ostringstream os;
    os << "My name is " << name;
    return os.str();
}

There are other alternate approaches if you need more generality. For example a class hierarchy where the base provides a "format" interface and child classes implement it with the appropriate varying implementation.

Answer 2

It might be overkill, but you can also take a look at boost::spirit, and more specifically, the 'karma' part which is a text generator.

Answer 3

Can you use sprintf?

There's also boost::format if you want to include boost.

Answer 4

For whom is still looking for such a library I have created a little one https://github.com/lexxmark/string_template.

    stpl::string_template st("Hello {{name}}!");
    st.set_arg("name", "World");
    auto r = st.render();
    EXPECT(r, "Hello World!");

It also has some nice customizations.

Answer 5

Update: The project has moved to Github and renamed into CTemplate: https://github.com/OlafvdSpek/ctemplate

From the new project page:

was originally called Google Templates, due to its origin as the template system used for Google search result pages. Now it has a more general name matching its community-owned nature.

---

Have you tried Google's CTemplate library ? It seems to be exactly what you are looking for: http://code.google.com/p/google-ctemplate/

Your example would be implemented like this:

In example.tpl:

My name is {{name}}

In example.cc:

#include <stdlib.h>
#include <string>
#include <iostream>
#include <google/template.h>

int main(int argc, char** argv)
{
  google::TemplateDictionary dict("example");
  dict.SetValue("name", "John Smith");
  google::Template* tpl = google::Template::GetTemplate("example.tpl",
                                                        google::DO_NOT_STRIP);
  std::string output;
  tpl->Expand(&output, &dict);
  std::cout << output;
  return 0;
}

Then:

$ gcc example.cc -lctemplate -pthread

$ ./a.out

My name is John Smith

Note that there is also a way to write templates as const strings if you don't want to bother writting your templates in separate files.

Answer 6

If you have many place holders, e.g if you have a macro template for a letter you want to be automatically expanded, some basic tokenization would be easier to maintain, implement and extend later. E.g

//pseudocode
foreach word in line
{
  if word=={{name}} print getFromDB(name,entry)
  else if word=={{address}} print getFromDB(address,entry)
  ..
  ..
  else print word

/*
* to get rid of if-else-if tree, you can just check if starts with {{ and ends with }} and directly query the string against a db/map/hash
*/

}

However, if the problem is a simple enough, and the template is small enough, just go for one of the answers mentioned above.