Swift报错：“‘nil‘ is incompatible with return type ‘User‘”

培根芝士2023-09-15 19:18

Swift 复制代码

func getUserById(userId: Int) -> User {
    if (userId != nil) {
        ...
    }
    return nil
}

上述代码报了一个错误："'nil' is incompatible with return type 'User'"，表示"nil"与返回类型"User"不兼容。

将返回值类型改为Optional类型User?

Swift 复制代码

func getUserById(userId: Int) -> User? {
    if (userId != nil) {
        ...
    }
    return nil
}

同理，如果调用getUserById(nil)的时候也会报错："'nil' is not compatible with expected argument type 'Int'"

将参数类型改为Int?即可

Swift 复制代码

func getUserById(userId: Int?) -> User? {
    if (userId != nil) {
        ...
    }
    return nil
}