@View
The @View decorator marks a method as read-only, meaning it cannot modify the contract's state. View methods are gas-free when called statically and are used to query contract data.
Syntax
@View
static methodName(param1: Type1, param2: Type2): ReturnType {
// Read-only implementation
}
Purpose
The @View decorator:
- Read-Only Access: Methods can only read state, not modify it
- Gas-Free Calls: No gas cost when called as static calls (queries)
- ABI Generation: Includes methods in ABI with "view" state mutability
- Query Interface: Provides external interface for data access
- No Transactions: Can be called without sending a transaction
Basic Example
@Contract
export class SimpleStorage {
static value: U256;
static owner: Address;
@View
static getValue(): U256 {
return value;
}
@View
static getOwner(): Address {
return owner;
}
@View
static isOwner(address: Address): Boolean {
return owner.equals(address);
}
}
Rules and Constraints
Read-Only Restriction
View methods cannot:
- Modify storage variables
- Emit events
- Call non-view external functions
- Create or modify contracts
@Contract
export class ViewExample {
static counter: U256;
@View
static getCounter(): U256 {
return counter; // ✅ Reading is allowed
}
@View
static invalidMethod(): U256 {
counter = U256Factory.fromString("10"); // ❌ Writing not allowed
SomeEvent.emit(); // ❌ Events not allowed
return counter;
}
}
Supported Operations
View methods can:
- Read storage variables
- Perform calculations
- Access blockchain data (block, msg info)
@Contract
export class Calculator {
static baseValue: U256;
@View
static calculate(multiplier: U256): U256 {
// ✅ All of these are allowed in view methods
const base = baseValue; // Read storage
const result = base.mul(multiplier); // Calculations
const timestamp = block.timestamp(); // Access blockchain data
return result.add(bonus);
}
@View
static getBonus(): U256 {
return U256Factory.fromString("100");
}
}
Advanced Usage
With Parameters
@Contract
export class Calculator {
static data: U256;
@View
static calculate(input: U256): U256 {
const two = U256Factory.fromString("2");
return input.add(two);
}
@View
static compare(a: U256, b: U256): Boolean {
return a.greaterThan(b);
}
@View
static getCurrentData(): U256 {
return data;
}
Step-by-Step Operations
@Contract
export class Calculator {
static counter: U256;
constructor() {
counter = U256Factory.fromString("10");
}
@View
static getCounter(): U256 {
return counter;
}
@View
static addNumbers(a: U256, b: U256): U256 {
const result: U256 = a.add(b);
return result;
}
@View
static calculateSum(limit: U256): U256 {
let total = U256Factory.create(); // 0
const one = U256Factory.fromString("1");
for (
let i = U256Factory.fromString("1");
i.lessThanOrEqual(limit);
i = i.add(one)
) {
total = total.add(i);
}
return total;
}
@View
static multiplyBySteps(base: U256, multiplier: U256): U256 {
let result = U256Factory.create();
const one = U256Factory.fromString("1");
for (
let count = U256Factory.create();
count.lessThan(multiplier);
count = count.add(one)
) {
result = result.add(base);
}
return result;
}
}
Gas Efficiency
View methods are gas-free when called as static calls:
// Called as static call (no gas)
const balance = await contract.balanceOf.staticCall(userAddress);
// Called in transaction (gas required)
const tx = await contract.someExternalMethod();
ABI Generation
View methods generate ABI entries with "view" state mutability:
{
"type": "function",
"name": "balanceOf",
"inputs": [
{"name": "account", "type": "address"}
],
"outputs": [
{"name": "", "type": "uint256"}
],
"stateMutability": "view"
}