Swift Playground报错：无法将‘Int’类型的值赋给‘[Int]’类型，求助实现数组相邻元素乘积功能

Hey there! Let's break down what's going wrong with your code and get it working exactly how you want it to.

First, the root of the error #

The message "Cannot assign value of type 'Int' to type '[Int]'" spells out the core issue clearly:

• newArray is declared as an array of integers ([Int]), but number[i] * number[i+1] gives you a single integer value. You can't assign a single number directly to an array—you need to add it to the array instead of overwriting it.

Second, a hidden crash waiting to happen #

Your loop uses 0...number.count-1, which means when i reaches the last index of number (that's 3 for your array), number[i+1] would try to access number[4]—an index that doesn't exist. This would crash your code even if you fixed the first error.

Here's the corrected code #

We'll use the append() method to add each calculated product to newArray, and adjust the loop range to avoid index out-of-bounds issues:

var number: [Int] = [1,2,3,4] 
var newArray: [Int] = [] 
// Loop from 0 up to (but not including) the second-to-last index
for i in 0..<number.count-1 { 
    let product = number[i] * number[i+1]
    newArray.append(product) // Add the product to the array instead of overwriting it
} 
print(newArray) // Output: [2, 6, 12] (matches your expected 1*2, 2*3, 3*4)

A more "Swifty" approach #

If you want cleaner, more idiomatic Swift code, you can skip the manual loop entirely and use built-in functions like zip and map:

let number = [1,2,3,4]
let newArray = zip(number, number.dropFirst()).map(*)
print(newArray) // Same output: [2, 6, 12]

Here's how this works:

• number.dropFirst() creates a copy of your array without the first element: [2,3,4]
• zip(number, number.dropFirst()) pairs elements from both arrays into tuples: (1,2), (2,3), (3,4)
• map(*) applies multiplication to each tuple, generating your final array of products.

内容的提问来源于stack exchange，提问作者Orhanko