@External
The @External decorator marks a method as publicly callable from outside the contract. External methods can be invoked through transactions and are included in the contract's ABI.
Syntax
@External
static methodName(param1: Type1, param2: Type2): ReturnType {
// Method implementation
}
Purpose
The @External decorator:
- Public Interface: Makes methods callable from external transactions
- ABI Generation: Includes the method in the contract's ABI
- State Modification: Can read and modify contract state
Basic Example
@Contract
export class SimpleStorage {
static value: U256;
@External
static setValue(newValue: U256): void {
value = newValue;
}
@External
static increment(): void {
const one = U256Factory.fromString("1");
value = value.add(one);
}
}
Rules and Constraints
Method Requirements
- Static Methods: External methods must be static
- Within Contract: Can only be used inside
@Contractdecorated classes - Supported Types: Parameters and return types must be supported by the ABI system
Type Support
Supported parameter and return types:
@External
static examples(
uintValue: U256, // ✅ Unsigned 256-bit integer
intValue: I256, // ✅ Signed 256-bit integer
addressValue: Address, // ✅ Ethereum address
stringValue: String, // ✅ Dynamic string
boolValue: Boolean // ✅ Boolean value
): U256 { // ✅ Any supported type as return
// Implementation
return uintValue;
}
// ❌ Unsupported types
@External
static invalid(complexObject: CustomClass): void { } // Error
Advanced Usage
With Return Values
@Contract
export class Calculator {
@External
static add(a: U256, b: U256): U256 {
return a.add(b);
}
@External
static subtract(a: U256, b: U256): U256 {
return a.sub(b);
}
@External
static double(value: U256): U256 {
const two = U256Factory.fromString("2");
return value.add(value);
}
}