# t00027 - Template decorator pattern
## Config
```yaml
diagrams:
  t00027_class:
    type: class
    glob:
      - t00027.cc
    using_namespace: clanguml::t00027
    include:
      namespaces:
        - clanguml::t00027

```
## Source code
File `tests/t00027/t00027.cc`
```cpp
#include <memory>
#include <tuple>
#include <type_traits>

namespace clanguml {
namespace t00027 {

class Shape {
public:
    virtual void display() = 0;
    virtual ~Shape() = default;
};

template <template <typename> class... T>
class Line : public Shape, public T<Line<>>... {
public:
    void display() override
    {
        std::apply([](auto &&...x) { (x.display(), ...); },
            std::forward_as_tuple(T<Line<>>()...));
    }
};

template <template <typename> class... T>
class Text : public Shape, public T<Text<>>... {
public:
    void display() override
    {
        std::apply([](auto &&...x) { (x.display(), ...); },
            std::forward_as_tuple(T<Text<>>()...));
    }
};

struct ShapeDecorator {
    virtual void display() = 0;
};

template <typename T> class Color : public ShapeDecorator {
public:
    void display() override { }
};

template <typename T> class Weight : public ShapeDecorator {
public:
    void display() override { }
};

struct Window {
    Line<Color, Weight> border;
    Line<Color> divider;
    Text<Color, Weight> title;
    Text<Color> description;
};
} // namespace t00027
} // namespace clanguml

```
## Generated PlantUML diagrams
![t00027_class](./t00027_class.svg "Template decorator pattern")
## Generated Mermaid diagrams
![t00027_class](./t00027_class_mermaid.svg "Template decorator pattern")
## Generated JSON models
```json
{
  "diagram_type": "class",
  "elements": [
    {
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      "display_name": "Shape",
      "id": "1593092483959332221",
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      "is_nested": false,
      "is_struct": false,
      "is_template": false,
      "is_union": false,
      "members": [],
      "methods": [
        {
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          "is_const": false,
          "is_consteval": false,
          "is_constexpr": false,
          "is_constructor": false,
          "is_copy_assignment": false,
          "is_coroutine": false,
          "is_defaulted": false,
          "is_deleted": false,
          "is_move_assignment": false,
          "is_noexcept": false,
          "is_operator": false,
          "is_pure_virtual": true,
          "is_static": false,
          "is_virtual": true,
          "name": "display",
          "parameters": [],
          "source_location": {
            "column": 18,
            "file": "t00027.cc",
            "line": 10,
            "translation_unit": "t00027.cc"
          },
          "type": "void"
        },
        {
          "access": "public",
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          "is_consteval": false,
          "is_constexpr": true,
          "is_constructor": false,
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          "is_defaulted": true,
          "is_deleted": false,
          "is_move_assignment": false,
          "is_noexcept": false,
          "is_operator": false,
          "is_pure_virtual": false,
          "is_static": false,
          "is_virtual": true,
          "name": "~Shape",
          "parameters": [],
          "source_location": {
            "column": 13,
            "file": "t00027.cc",
            "line": 11,
            "translation_unit": "t00027.cc"
          },
          "type": "void"
        }
      ],
      "name": "Shape",
      "namespace": "clanguml::t00027",
      "source_location": {
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        "file": "t00027.cc",
        "line": 8,
        "translation_unit": "t00027.cc"
      },
      "template_parameters": [],
      "type": "class"
    },
    {
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      "id": "1568932879061562228",
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      "is_union": false,
      "members": [],
      "methods": [],
      "name": "Line",
      "namespace": "clanguml::t00027",
      "source_location": {
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        "file": "t00027.cc",
        "line": 15,
        "translation_unit": "t00027.cc"
      },
      "template_parameters": [],
      "type": "class"
    },
    {
      "bases": [
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        {
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          "is_virtual": false,
          "name": "clanguml::t00027::Line::T<clanguml::t00027::Line>"
        }
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      },
      "template_parameters": [
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    {
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    {
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    {
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  ],
  "name": "t00027_class",
  "package_type": "namespace",
  "relationships": [
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      "source": "1373544984027721472",
      "type": "aggregation"
    }
  ],
  "using_namespace": "clanguml::t00027"
}
```