mstch/README.md

# mstch - {{mustache}} templates in C++11 

![mstch logo](http://i.imgur.com/MRyStO5.png)

mstch is a complete implementation of [{{mustache}}](http://mustache.github.io/) 
templates using modern C++. It's compliant with [specifications](https://github.com/mustache/spec)
v1.1.3, including the lambda module.

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## Supported features

mstch supports the complete feature set described in the `mustache(5)` [manpage](http://mustache.github.com/mustache.5.html):

 - JSON-like data structure using [Boost.Variant](http://www.boost.org/libs/variant)
 - variables, sections, inverted sections
 - partials
 - changing the delimiter
 - C++11 lambdas
 - C++ objects as view models

## Basic usage

```c++
#include <iostream>
#include <mstch/mstch.hpp>

int main() {
  std::string view{"{{#names}}Hi {{name}}!\n{{/names}}"};
  mstch::map context{
    {"names", mstch::array{
      mstch::map{{"name", std::string{"Chris"}}},
      mstch::map{{"name", std::string{"Mark"}}},
      mstch::map{{"name", std::string{"Scott"}}},
    }}
  };
  
  std::cout << mstch::render(view, context) << std::endl;
  
  return 0;
}

```

The output of this example will be:

```html
Hi Chris!
Hi Mark!
Hi Scott!
```

### Data structure

The types in the example above, `mstch::array` and `mstch::map` are  actually 
aliases for standard types:

```c++
using map = std::map<const std::string, node>;
using array = std::vector<node>;
```

`mstch::node` is a `boost::variant` that can hold a `std::string`, `int`, 
`double`, `bool`, `mstch::lambda` or a `std::shared_ptr<mstch::object>` 
(see below), also a map or an array recursively. Essentially it works just like 
a JSON object.

Note that when using a `std::string` as value you must explicitly specify the 
type, since a `const char*` literal like `"foobar"` would be implicitly 
converted to `bool`. Alternatively you can use [C++14 string_literals](http://en.cppreference.com/w/cpp/string/basic_string/operator%22%22s)
if your compiler supports it.

## Advanced usage

### Partials

Partials can be passed in a `std::map` as the third parameter of the 
`mstch::render` function:

```c++
std::string view{"{{#names}}{{> user}}{{/names}}"};
std::string user_view{"<strong>{{name}}\n</strong>"};
mstch::map context{
  {"names", mstch::array{
    mstch::map{{"name", std::string{"Chris"}}},
    mstch::map{{"name", std::string{"Mark"}}},
    mstch::map{{"name", std::string{"Scott"}}},
  }}
};
  
std::cout << mstch::render(view, context, {{"user", user_view}}) << std::endl;
```

Output:

```html
<strong>Chris</strong>
<strong>Mark</strong>
<strong>Scott</strong>
```

### Lambdas

C++11 lambda expressions can be used to add logic to your templates. Like a
`const char*` literal, lambdas can be implicitly converted to `bool`, so they
must be wrapped in a `mstch::lambda` object when used in a `mstch::node`. The 
lambda expression passed to `mstch::lambda` must itself return a `mstch::node`.
The returned node will be rendered to a string, then it will be parsed as a
template.

The lambda expression accepts either no parameters:

```c++
std::string view{"Hello {{lambda}}!"};
mstch::map context{
  {"lambda", mstch::lambda{[]() -> mstch::node {
    return std::string{"World"};
  }}}
};

std::cout << mstch::render(view, context) << std::endl;
```

Output:

```html
Hello World!
```

Or it accepts a `const std::string&` that gets the unrendered literal block:

```c++
std::string view{"{{#bold}}{{yay}} :){{/bold}}"};
mstch::map context{
  {"yay", std::string{"Yay!"}},
  {"bold", mstch::lambda{[](const std::string& text) -> mstch::node {
    return "<b>" + text + "</b>";
  }}}
};

std::cout << mstch::render(view, context) << std::endl;
```

Output:

```html
<b>Yay! :)</b>
```

### Objects

Custom objects can also be used as context for rendering templates. The class 
must inherit from `mstch::object`, and register it's exported methods with
`register_methods`. Exported methods must have the return type of `mstch::node`.
Objects must be created as a `std::shared_ptr`.

```c++
class example: public mstch::object {
 public:
  example(): m_value(1) {
    register_methods(this, {
      {"count", &example::count},
      {"names", &example::names}  
    });
  }
  
  mstch::node count() {
    return m_value++;
  }
  
  mstch::node names() {
    return mstch::array{
      std::string{"Chris"}, std::string{"Mark"}, std::string{"Scott"}};
  }
  
 private:
  int m_value;
};

std::string view{"{{#names}}<b>{{count}}</b>: {{.}}\n{{/names}}"};
const auto context = std::make_shared<example>();

std::cout << mstch::render(view, context) << std::endl;
```

Output:

```html
<b>1</b>: Chris
<b>2</b>: Mark
<b>3</b>: Scott
```

### Custom escape function

By default, mstch uses HTML escaping on the output, as per specification. This
is not useful if your output is not HTML, so mstch provides a way to supply
your own escape implementation. Just assign any callable object to the static
`mstch::config::escape`, which is an initially empty
`std::function<std::string(const std::string&)>`. 

For example you can turn off escaping entirely with a lambda:

```c++
mstch::config::escape = [](const std::string& str) -> std::string {
  return str;
};
```

## Requirements

 - A C++ compiler with decent C++11 support. Currently tested with:
   - GCC 4.7, 4.8, 4.9, 5.1
   - clang 3.5, 3.6, 3.7 (both libstdc++ and libc++ are supported)
   - MSVC 2013, 2015
 - Boost 1.54+ for [Boost.Variant](http://www.boost.org/libs/variant)
 - CMake 3.0+ for building

## Using mstch in your project

If you are using CMake, the easiest way to include mstch in your project is to 
copy the whole directory to your source tree, and use `add_subdirectory` in your 
CMakeLists.txt. This will set a variable named `mstch_INCLUDE_DIR` that contains 
its include path, and add a static library target named `mstch`. For example:

```cmake
add_subdirectory(external/mstch)
include_directories(${mstch_INCLUDE_DIR})
target_link_libraries(your_project mstch)
```

If you prefer to install the library globally, you can simply do the following 
from the root of the source tree:

```bash
 $ mkdir build
 $ cd build
 $ cmake ..
 $ make
 $ make install
```

The install command may require root privileges. This will also install CMake 
config files, so you can use use `find_package` in your CMakeLists.txt:

```cmake
find_package(mstch)
target_link_libraries(your_project mstch::mstch)
```

## Running the unit tests

Unit tests are using the [Catch](https://github.com/philsquared/Catch) framework
and [rapidjson](http://rapidjson.org/) to parse the
[Mustache specifications](https://github.com/mustache/spec), all of which are 
included in the repository as git submodules. Various 
[Boost](http://www.boost.org/) libraries are also required to build them.

Don't forget to initialize submodules:

```bash
 $ git submodule init
 $ git submodule update
```

To build and run the unit tests:

```bash
 $ mkdir build
 $ cd build
 $ cmake -DWITH_UNIT_TESTS=ON ..
 $ make
 $ make test
```

## License

mstch is licensed under the [MIT license](https://github.com/no1msd/mstch/blob/master/LICENSE).