Immutable Variable
A smart-contract variable assigned during deployment and then fixed for the contract's lifetime.
Explain Like I'm 12
A smart-contract variable assigned during deployment and then fixed for the contract's lifetime.
Why It Matters
Smart-contract concepts are essential for understanding programmable blockchain applications.
How It Works
The developer declares a state variable with the 'immutable' keyword within the contract scope. Inside the constructor function, the developer assigns a value to this variable based on inputs or other logic. During compilation, the Solidity compiler replaces references to the variable with the assigned value directly in the runtime code.
Real-World Example
A decentralized exchange deploying a factory contract might set the address of a specific fee-collection contract as an immutable variable during deployment.
Advantages
- Reduced gas costs for read operations
- Guaranteed value persistence after deployment
- Prevents accidental state modification
Limitations
- Cannot be changed after deployment
- Limited to specific data types
- Restricted assignment inside constructor only
Common Misconceptions
- People often think immutable variables are the same as constants, but constants must be fixed at compile-time.
- Many users assume immutable variables can be updated via administrative functions, but they are physically locked.
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Related Terms
ABI
An Application Binary Interface defines how external software encodes calls to and decodes results from a smart contract.
EVM
The Ethereum Virtual Machine (EVM) is a decentralized, Turing-complete computation engine that executes smart contracts on the Ethereum network. It functions as a global state machine, where the state is updated based on code execution on the blockchain. Because the EVM is implemented by every node in the network, it ensures that smart contracts run exactly as intended across all devices, regardless of local hardware differences. This allows for complex, programmable logic to be embedded into the blockchain.
Smart Contract
A smart contract is a self-executing program stored on a blockchain that automatically runs when predetermined conditions are met. These contracts eliminate the need for intermediaries by encoding terms directly into lines of code, ensuring that the agreement is enforced exactly as written without human interference. Because they reside on an immutable ledger, the execution results are verifiable, transparent, and impossible to tamper with once deployed.
Smart Contract
A self-executing program stored on a blockchain that automatically enforces and executes the terms of an agreement when predetermined conditions are met. Smart contracts are deterministic, immutable once deployed, and form the backbone of decentralized applications.
Solidity
Solidity is the primary high-level, object-oriented programming language used for writing smart contracts that execute on the Ethereum Virtual Machine (EVM). It is statically typed and supports inheritance, libraries, and complex user-defined types. Solidity was designed specifically for blockchain environments to facilitate the creation of self-executing contracts with contract-based accountability. It is heavily influenced by C++, Python, and JavaScript, making it relatively accessible to developers coming from traditional software engineering backgrounds who are transitioning into the Web3 ecosystem.