> 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::Component

> Common class for all non-Operator components.

Common class for all non-Operator components.

This class is the base class for all non-Operator components including [`holoscan::Condition`](condition), [`holoscan::Resource`](resource), [`holoscan::NetworkContext`](networkcontext), [`holoscan::Scheduler`](scheduler) It is used to define the common interface for all components.

[`holoscan::Operator`](operator) does not inherit from this class as it uses [`holoscan::OperatorSpec`](operatorspec) instead of [`holoscan::ComponentSpec`](componentspec).

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

**Inherits from:** `holoscan::ComponentBase` (public)

---

## Methods

### set\_parameters \[#setparameters]

```cpp showLineNumbers={false}
virtual void holoscan::Component::set_parameters()
```

Set the parameters based on defaults (sets GXF parameters for GXF operators).

### spec \[#spec]

#### Set the component spec

```cpp showLineNumbers={false}
Component & holoscan::Component::spec(
    const std::shared_ptr<ComponentSpec> &spec
)
```

Set the component spec.

**Returns:** The reference to this component.

**Parameters**

**`spec`** `const std::shared_ptr<ComponentSpec> &`

The component spec.

---

#### Get a pointer to the component spec

```cpp showLineNumbers={false}
ComponentSpec * holoscan::Component::spec()
```

Get a pointer to the component spec.

**Returns:** The pointer to the component spec.

### spec\_shared \[#specshared]

```cpp showLineNumbers={false}
std::shared_ptr<ComponentSpec> holoscan::Component::spec_shared()
```

Get a shared pointer to the component spec.

**Returns:** The shared pointer to the component spec.

### id \[#id]

```cpp showLineNumbers={false}
int64_t holoscan::Component::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::Component::name() const
```

Get the name of the component.

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

### fragment \[#fragment]

#### Get a pointer to \[Fragment]\(fragment) object

inline

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

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

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

#### Const

inline

const

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

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

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

#### Set the fragment that owns this component

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

Set the fragment that owns this component.

### add\_arg \[#addarg]

#### Add an argument to the component (1)

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

Add an argument to the component.

**Parameters**

**`arg`** `const Arg &`

The argument to add.

---

#### Add an argument to the component (2)

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

Add an argument to the component.

**Parameters**

**`arg`** `Arg &&`

The argument to add.

---

#### Add a list of arguments to the component (1)

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

Add a list of arguments to the component.

**Parameters**

**`arg`** `const ArgList &`

The list of arguments to add.

---

#### Add a list of arguments to the component (2)

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

Add a list of arguments to the component.

**Parameters**

**`arg`** `ArgList &&`

The list of arguments to add.

---

### args \[#args]

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

Get the list of arguments.

**Returns:** The vector of arguments.

### initialize \[#initialize]

```cpp showLineNumbers={false}
virtual void holoscan::Component::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::Component::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::Component::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::Component::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**

**`ServiceT`** `typename`

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**

**`id`** `std::string_view` — default: ""

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::Component::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**

**`service_type`** `const std::type_info &`

The type info of the service/resource to retrieve.

---

**`id`** `std::string_view` — default: ""

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

---

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

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

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

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

#### Update parameters based on the specified arguments

```cpp showLineNumbers={false}
void holoscan::Component::update_params_from_args()
```

Update parameters based on the specified arguments.

#### Update parameters based on the specified arguments (with params)

```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::Component::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::Component::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**

**`typeT`** `typename`

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::Component::register_argument_setter()
```

Register the argument setter for the given type.

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

**Template parameters**

**`typeT`** `typename`

The type of the argument to register.

---

---

## Member variables

| Name                | Type                               | Description                                       |
| ------------------- | ---------------------------------- | ------------------------------------------------- |
| `spec_`             | `std::shared_ptr< ComponentSpec >` | The component specification.                      |
| `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.                  |