> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.nvidia.com/holoscan/sdk-user-guide/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.nvidia.com/holoscan/sdk-user-guide/_mcp/server.

# holoscan::ComponentBase

> Base class for all components.

Base class for all components.

This class is the base class for all components including [`holoscan::Operator`](operator), [`holoscan::Condition`](condition), and [`holoscan::Resource`](resource). It is used to define the common interface for all components.

```cpp showLineNumbers={false}
#include <holoscan/component.hpp>
```

***

## Constructors

### ComponentBase \[#componentbase]

```cpp showLineNumbers={false}
holoscan::ComponentBase::ComponentBase() = default
```

inline

explicit

```cpp showLineNumbers={false}
template <typename ArgT,
          typename... ArgsT,
          typename = std::enable_if_t<   !std::is_base_of_v<::holoscan::ComponentBase, std::decay_t<ArgT>> &&   (std::is_same_v<::holoscan::Arg, std::decay_t<ArgT>> ||   std::is_same_v<::holoscan::ArgList, std::decay_t<ArgT>>)>>
holoscan::ComponentBase::ComponentBase(
    ArgT &&arg,
    ArgsT &&... args
)
```

Construct a new [Component](component) object.

**Parameters**

The first argument to be passed to the component.

The remaining arguments to be passed to the component.

### Destructor \[#destructor]

### \~ComponentBase

```cpp showLineNumbers={false}
virtual holoscan::ComponentBase::~ComponentBase() = default
```

***

## Methods

### id \[#id]

```cpp showLineNumbers={false}
int64_t holoscan::ComponentBase::id() const
```

Get the identifier of the component.

By default, the identifier is set to -1. It is set to a valid value when the component is initialized.

With the default executor (GXFExecutor), the identifier is set to the GXF component ID.

**Returns:** The identifier of the component.

### name \[#name]

```cpp showLineNumbers={false}
const std::string & holoscan::ComponentBase::name() const
```

Get the name of the component.

**Returns:** The name of the component.

### fragment \[#fragment]

inline

```cpp showLineNumbers={false}
Fragment * holoscan::ComponentBase::fragment()
```

Get a pointer to [Fragment](fragment) object.

**Returns:** The Pointer to [Fragment](fragment) object.

inline

const

```cpp showLineNumbers={false}
const Fragment * holoscan::ComponentBase::fragment() const
```

Get a const pointer to [Fragment](fragment) object.

**Returns:** The const pointer to [Fragment](fragment) object.

```cpp showLineNumbers={false}
void holoscan::ComponentBase::fragment(
    Fragment *frag
)
```

Set the fragment that owns this component.

### add\_arg \[#addarg]

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    const Arg &arg
)
```

Add an argument to the component.

**Parameters**

The argument to add.

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    Arg &&arg
)
```

Add an argument to the component.

**Parameters**

The argument to add.

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    const ArgList &arg
)
```

Add a list of arguments to the component.

**Parameters**

The list of arguments to add.

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    ArgList &&arg
)
```

Add a list of arguments to the component.

**Parameters**

The list of arguments to add.

### args \[#args]

```cpp showLineNumbers={false}
std::vector<Arg> & holoscan::ComponentBase::args()
```

Get the list of arguments.

**Returns:** The vector of arguments.

### initialize \[#initialize]

```cpp showLineNumbers={false}
virtual void holoscan::ComponentBase::initialize()
```

Initialize the component.

This method is called only once when the component is created for the first time, and use of light-weight initialization.

### to\_yaml\_node \[#toyamlnode]

```cpp showLineNumbers={false}
virtual YAML::Node holoscan::ComponentBase::to_yaml_node() const
```

Get a `YAML` representation of the component.

**Returns:** `YAML` node including the id, name, fragment name, and arguments of the component.

### description \[#description]

```cpp showLineNumbers={false}
std::string holoscan::ComponentBase::description() const
```

Get a description of the component.

**Returns:** `YAML` string.

**See also:**
to\_yaml\_node()

### service \[#service]

```cpp showLineNumbers={false}
template <typename ServiceT = DefaultFragmentService>
std::shared_ptr<ServiceT> holoscan::ComponentBase::service(
    std::string_view id = ""
) const
```

Retrieve a registered fragment service or resource.

Retrieves a previously registered fragment service or resource by its type and optional identifier. Returns nullptr if no service/resource is found with the specified type and identifier.

Note that any changes to the service retrieval logic in this method should be synchronized with the implementation in `Fragment::service()` method to maintain consistency.

**Returns:** The shared pointer to the service/resource, or nullptr if not found or if type casting fails.

**Template parameters**

The type of the service/resource to retrieve. Must inherit from either [Resource](resource) or [FragmentService](fragmentservice). Defaults to [DefaultFragmentService](defaultfragmentservice) if not specified.

**Parameters**

The identifier of the service/resource. If empty, retrieves by type only.

### get\_service\_by\_type\_info \[#getservicebytypeinfo]

```cpp showLineNumbers={false}
std::shared_ptr<FragmentService> holoscan::ComponentBase::get_service_by_type_info(
    const std::type_info &service_type,
    std::string_view id = ""
) const
```

Retrieve a registered fragment service or resource for Python bindings.

This is a helper method for Python bindings to retrieve a service by its C++ type info.

**Returns:** The shared pointer to the base service, or nullptr if not found.

**Parameters**

The type info of the service/resource to retrieve.

The identifier of the service/resource. If empty, retrieves by type only.

### reset\_backend\_objects \[#resetbackendobjects]

```cpp showLineNumbers={false}
virtual void holoscan::ComponentBase::reset_backend_objects()
```

Reset any backend-specific objects (e.g. GXF GraphEntity).

### update\_params\_from\_args \[#updateparamsfromargs]

```cpp showLineNumbers={false}
void holoscan::ComponentBase::update_params_from_args(
    std::unordered_map<std::string, ParameterWrapper> &params
)
```

Update parameters based on the specified arguments.

### service\_provider \[#serviceprovider]

```cpp showLineNumbers={false}
void holoscan::ComponentBase::service_provider(
    FragmentServiceProvider *provider
)
```

Set the service provider that owns this component.

***

## Static methods

### register\_converter \[#registerconverter]

```cpp showLineNumbers={false}
template <typename typeT>
static void holoscan::ComponentBase::register_converter()
```

Register the argument setter for the given type.

If an operator or resource has an argument with a custom type, the argument setter must be registered using this method.

The argument setter is used to set the value of the argument from the `YAML` configuration.

This method can be called in the initialization phase of the operator/resource (e.g., `initialize()`). The example below shows how to register the argument setter for the custom type (`Vec3`):

It is assumed that `YAML::convert<T>::encode` and `YAML::convert<T>::decode` are implemented for the given type. You need to specialize the `YAML::convert<>` template class.

For example, suppose that you had a `Vec3` class with the following members:

You can define the `YAML::convert<Vec3>` as follows in a '.cpp' file:

Please refer to the [yaml-cpp documentation](https://github.com/jbeder/yaml-cpp/wiki/Tutorial#converting-tofrom-native-data-types) for more details.

**Template parameters**

The type of the argument to register.

**Example**

```cpp showLineNumbers={false}
void MyOp::initialize() {
  register_converter<Vec3>();
}
```

**Example**

```cpp showLineNumbers={false}
struct Vec3 {
  // make sure you have overloaded operator==() for the comparison
  double x, y, z;
};
```

**Example**

```cpp showLineNumbers={false}
namespace YAML {
template<>
struct convert<Vec3> {
  static Node encode(const Vec3& rhs) {
    Node node;
    node.push_back(rhs.x);
    node.push_back(rhs.y);
    node.push_back(rhs.z);
    return node;
  }

  static bool decode(const Node& node, Vec3& rhs) {
    if(!node.IsSequence() || node.size() != 3) {
      return false;
    }

    rhs.x = node[0].as<double>();
    rhs.y = node[1].as<double>();
    rhs.z = node[2].as<double>();
    return true;
  }
};
}
```

### register\_argument\_setter \[#registerargumentsetter]

```cpp showLineNumbers={false}
template <typename typeT>
void holoscan::ComponentBase::register_argument_setter()
```

Register the argument setter for the given type.

Please refer to the documentation of `register_converter()` for more details.

**Template parameters**

The type of the argument to register.

***

## Member variables

| Name                | Type                        | Description                                       |
| ------------------- | --------------------------- | ------------------------------------------------- |
| `id_`               | `int64_t`                   | The ID of the component.                          |
| `name_`             | `std::string`               | Name of the component.                            |
| `fragment_`         | `Fragment *`                | Pointer to the fragment that owns this component. |
| `args_`             | `std::vector< Arg >`        | List of arguments.                                |
| `service_provider_` | `FragmentServiceProvider *` | Pointer to the service provider.                  |