迅速处理无[重复]

Question

我是Swift新手，这段代码给了我一个错误，尽管它没有文本，但它还是通过了“lastname！=nil”。

线程1：致命错误：在展开一个可选值时意外地找到nil

func imageFromInitials(firstName: String?, lastName: String?, withBlock: @escaping (_ image: UIImage) -> Void) {

var string: String!
var size = 36

if firstName != nil && lastName != nil {
    string = String(firstName!.first!).uppercased() + String(lastName!.first!).uppercased()
} else {
    string = String(firstName!.first!).uppercased()
    size = 72
}

我很困惑，不知道为什么验证不起作用

Answer 1

字符串为空与为零并不相同。您还需要检查字符串是否为空，或者只是安全地打开名字和姓氏的第一个字符：

func imageFromInitials(firstName: String?,
                       lastName: String?,
                       withBlock block: @escaping (_ image: UIImage) -> Void) {
    let string: String
    let size: Int

    if let firstInitial = firstName?.first {
        if let lastInitial = lastName?.first {
            string = (String(firstInitial) + String(lastInitial)).uppercased()
            size = 36
        } else {
            string = String(firstInitial).uppercased()
            size = 72
        }
    } else {
        string = ""
        size = 36
    }

    // the rest of your function
}

或者，如果您想用一种更“快速的™”的方式来完成它（如果您可以在只提供lastname的情况下生成一个非空的字符串)，那么您可以这样做：

func imageFromInitials(firstName: String?,
                       lastName: String?,
                       withBlock block: @escaping (_ image: UIImage) -> 
    let string = [firstName, lastName]
        .compactMap { $0?.first }
        .map { String($0) }
        .joined()
        .uppercased()

    let size = string.count == 1 ? 72 : 36

    // the rest of your function
}