值类型
uint、address、bool、bytes
值类型 是 CoddyKit 上的免费 Web3 & DApp Development Fundamentals 课时。 这是第 1 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Web3 & DApp Development Fundamentals 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Web3 & DApp Development Fundamentals 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
What Are Value Types?
Value types in Solidity hold their data directly and are copied whenever they are assigned to a variable or passed to a function.
This is different from reference types (arrays, structs, mappings) which point to a shared location. Value types include bool, integers, address, and fixed-size bytes.
- Always copied on assignment
- Stored compactly
- Predictable gas cost
Booleans
The bool type holds either true or false. It is the result of comparison and logical operators.
Solidity supports ! (not), && (and), || (or). Logical operators short-circuit, just like in most languages.
<code>bool isActive = true;
bool hasPaid = false;
bool ready = isActive && !hasPaid;</code>Unsigned Integers
uint stores non-negative whole numbers. uint is an alias for uint256.
You can choose smaller sizes in steps of 8 bits: uint8, uint16, ... up to uint256. Smaller types can save storage when packed together in a struct.
<code>uint256 balance = 1000;
uint8 smallCount = 255; // max value for uint8</code>Signed Integers
int stores values that can be negative or positive. int is an alias for int256.
An int8 ranges from -128 to 127. Use signed integers only when negatives are genuinely possible, since they are easy to misuse.
<code>int256 temperature = -15;
int8 delta = 100;</code>Overflow Protection
Since Solidity 0.8.0, arithmetic automatically reverts on overflow and underflow. You no longer need SafeMath for basic safety.
If you intentionally want wrapping behavior for gas savings, wrap the math in an unchecked block.
<code>uint8 x = 255;
// x + 1 would revert (overflow)
unchecked {
x = x + 1; // wraps to 0
}</code>The address Type
An address holds a 20-byte Ethereum account identifier. It can refer to a wallet (EOA) or a contract.
The address type exposes members like .balance (in wei) and methods such as .transfer() and .send().
<code>address owner = 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4;
uint256 bal = owner.balance;</code>address vs address payable
A plain address cannot receive Ether directly. To send funds you need address payable, which adds .transfer() and .send().
You convert between them explicitly with payable(addr).
<code>address recipient = msg.sender;
address payable wallet = payable(recipient);
wallet.transfer(1 ether);</code>Fixed-Size Bytes
Solidity offers fixed-size byte arrays from bytes1 to bytes32. These are value types and are cheaper than dynamic bytes when the length is known.
They are useful for hashes, identifiers, and short fixed data.
<code>bytes32 hash = keccak256(abi.encodePacked('hello'));
bytes1 firstByte = hash[0];</code>Enums
An enum defines a custom type with a fixed set of named constants. Internally each value is a small uint starting at 0.
Enums make state machines readable, such as the status of an order.
<code>enum Status { Pending, Shipped, Delivered }
Status public current = Status.Pending;
function ship() public {
current = Status.Shipped;
}</code>Literals and Units
Solidity provides handy unit suffixes. Ether units: wei, gwei, ether. Time units: seconds, minutes, hours, days, weeks.
1 ether equals 10**18 wei.
<code>uint256 fee = 1 ether; // 1000000000000000000 wei
uint256 timeout = 2 days; // 172800 seconds</code>Default Values
Solidity has no null. Every value type has a zero default: uint is 0, bool is false, address is the zero address 0x0...0.
Checking against the zero address is a common guard.
<code>address public admin; // defaults to address(0)
function setAdmin(address a) public {
require(a != address(0), 'zero address');
admin = a;
}</code>Quick Check
Test your understanding of Solidity value types.
Recap
You learned the core value types in Solidity:
boolfor true/false logicuint/intwith built-in overflow protection since 0.8.0addressandaddress payablefor accounts and transfers- Fixed
bytesN,enum, and unit literals like1 ether
Remember: value types are copied, and every type has a zero default value.
常见问题解答
「值类型」课时是免费的吗？
是的 — 「值类型」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Web3 & DApp Development Fundamentals 课程的其余内容，请升级到 CoddyKit PRO。 Web3 & DApp Development Fundamentals 课程共包含 4 节课。
「值类型」这节课中我会学到什么？
uint、address、bool、bytes 你通过在浏览器中直接运行的动手代码来练习 Web3 & DApp Development Fundamentals，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Web3 & DApp Development Fundamentals 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Web3 & DApp Development Fundamentals 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 1 节课，共 4 节。
「值类型」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Web3 & DApp Development Fundamentals 课中编写并运行代码吗？
能。每节 Web3 & DApp Development Fundamentals 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。