控制结构与循环
掌握条件语句（if/else）和各种循环结构（for、while），实现动态的合约行为。
控制结构与循环 是 CoddyKit 上的免费 Blockchain Smart Contracts with Solidity 课时。 这是第 2 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 Blockchain Smart Contracts with Solidity 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Blockchain Smart Contracts with Solidity 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。
Control Structures Intro
Welcome to Lesson 2! Today, we'll learn about control structures in Solidity. These are essential for making your smart contracts dynamic and responsive.
Control structures allow your contract to:
- Make decisions based on conditions.
- Repeat actions multiple times.
- Execute different code paths.
Think of them as the 'brain' of your contract, guiding its behavior.
Conditional 'if' Statements
The simplest control structure is the if statement. It executes a block of code only if a specified condition is true.
The condition must evaluate to a bool (true or false). If true, the code inside the curly braces {} runs; otherwise, it's skipped.
'if-else' for Alternatives
Often, you want to perform one action if a condition is true and a different action if it's false. This is where the if-else statement comes in.
If the if condition is true, its block executes. If false, the code in the else block executes instead. Only one of the two blocks will ever run.
'else if' for Multiple Choices
What if you have more than two possible outcomes? Use else if to check multiple conditions sequentially.
The contract checks each condition in order. The first one that evaluates to true will have its code block executed, and all subsequent else if and else blocks are skipped.
Conditional Logic Example
Let's see if-else if-else in action. This contract checks if a number is positive, negative, or zero.
Try calling checkNumber with different integer values like 5, -3, or 0.
pragma solidity ^0.8.0;
contract ConditionalChecker {
function checkNumber(int _number) public pure returns (string memory) {
if (_number > 0) {
return "Positive";
} else if (_number < 0) {
return "Negative";
} else {
return "Zero";
}
}
}Introducing Loops
Sometimes you need to repeat a block of code multiple times. This is called looping, and it's super efficient!
Loops are useful for:
- Iterating over arrays or lists.
- Performing calculations multiple times.
- Waiting for a condition to be met.
Solidity provides for and while loops.
The 'for' Loop
The for loop is perfect when you know exactly how many times you want to repeat an action. It has three parts:
- Initialization: Sets up a counter (e.g.,
uint i = 0). - Condition: The loop continues as long as this is true (e.g.,
i < 10). - Increment/Decrement: Changes the counter after each iteration (e.g.,
i++).
Runnable 'for' Loop
Here's a for loop example that calculates the sum of numbers up to a given limit. This shows how to accumulate a value over several iterations.
Try calling calculateSum with a small number like 5.
pragma solidity ^0.8.0;
contract ForLoopDemo {
// Calculates the sum of numbers from 1 up to _limit
function calculateSum(uint _limit) public pure returns (uint) {
uint total = 0;
for (uint i = 1; i <= _limit; i++) {
total += i;
}
return total;
}
}The 'while' Loop
The while loop is ideal when you don't know exactly how many times the loop needs to run, but you have a specific condition that must be met to stop.
The loop continues as long as its condition is true. Be careful to ensure the condition eventually becomes false to avoid infinite loops!
Runnable 'while' Loop
This example demonstrates a simple countdown using a while loop. The loop continues as long as currentCount is greater than zero.
Call simpleCountdown with a value like 3. It will return 0 after completing the countdown.
pragma solidity ^0.8.0;
contract WhileLoopDemo {
// Counts down from a starting number to zero
function simpleCountdown(uint _start) public pure returns (uint) {
uint currentCount = _start;
while (currentCount > 0) {
currentCount--; // Decrement counter
}
return currentCount; // Will be 0 when loop finishes
}
}Check Your Understanding
Consider the following Solidity contract function:
pragma solidity ^0.8.0;
contract ScoreChecker {
function getStatus(uint _score) public pure returns (string memory) {
if (_score >= 90) {
return "Excellent";
} else if (_score >= 70) {
return "Good";
} else if (_score >= 50) {
return "Pass";
} else {
return "Fail";
}
}
}Recap: Control & Loops
Great job! You've mastered the fundamentals of control structures and loops in Solidity.
- Conditional statements (
if,else if,else) allow your contract to make decisions. - Loops (
for,while) enable repetitive execution of code blocks.
These tools are crucial for building smart contracts that can react dynamically and perform complex operations. Next, we'll dive into functions and visibility modifiers!
常见问题解答
「控制结构与循环」课时是免费的吗？
是的 — 「控制结构与循环」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 Blockchain Smart Contracts with Solidity 课程的其余内容，请升级到 CoddyKit PRO。 Blockchain Smart Contracts with Solidity 课程共包含 4 节课。
「控制结构与循环」这节课中我会学到什么？
掌握条件语句（if/else）和各种循环结构（for、while），实现动态的合约行为。 你通过在浏览器中直接运行的动手代码来练习 Blockchain Smart Contracts with Solidity，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 Blockchain Smart Contracts with Solidity 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Blockchain Smart Contracts with Solidity 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 2 节课，共 4 节。
「控制结构与循环」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 Blockchain Smart Contracts with Solidity 课中编写并运行代码吗？
能。每节 Blockchain Smart Contracts with Solidity 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。