> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Dart Required Named Parameter
A required named parameter in Dart is a named function or constructor parameter that mandates an explicit argument at the call site. Enforced by the `required` modifier, it guarantees that a value is passed during invocation, allowing the parameter to be strongly typed as non-nullable without necessitating a default value.
## Syntax
Required named parameters are declared inside curly braces `{}` using the `required` keyword preceding the type declaration.
```dart theme={"dark"}
void configureConnection({required String host, required int port}) {
print('Connecting to $host:$port');
}
// Valid invocation (order independent)
configureConnection(port: 8080, host: 'localhost');
// Invalid invocation (compile-time error: missing 'port')
// configureConnection(host: 'localhost');
```
## Technical Mechanics
* **Compile-Time Enforcement:** The Dart analyzer strictly enforces the presence of the parameter. Failing to provide a required named parameter results in a compile-time error, not a runtime exception.
* **Null Safety Interaction:** By default, named parameters in Dart are optional. Under sound null safety, optional parameters must either be nullable (e.g., `String?`) or have a default value. The `required` modifier overrides this, allowing a named parameter to be non-nullable (e.g., `String`) without a default value.
* **Explicit Nullability:** A parameter can be both `required` and nullable (`Type?`). In this scenario, the caller is still forced to explicitly pass an argument, even if that argument is explicitly `null`.
* **Position Independence:** Like all named parameters, required named parameters do not rely on positional arguments and can be passed in any order at the call site.
* **Mixing Parameter Types:** Required named parameters can be freely mixed with optional named parameters within the same `{}` block.
## Advanced Declaration Example
```dart theme={"dark"}
void executeOperation(
String operationId, { // Positional parameter
required String environment, // Required, non-nullable
required String? authKey, // Required, explicitly nullable
int timeout = 3000, // Optional, default value provided
}) {
// Function body
}
// Caller must explicitly provide 'environment' and 'authKey'
executeOperation(
'op-123',
authKey: null,
environment: 'production',
);
```
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