ios - unexpectedly found nil while unwrapping an Optional value

Question

调试时遇到的问题错误，求解决办法

PHP中文网 · Answer

Looking at this error description, the questioner probably forcibly unpacked the optional variables, right? Forced unpacking must ensure that the variable value is not empty, otherwise an error will be reported. The insurance method is as follows:

var a:Int?
if let a1 = a {
    //如果a非空，就会将a的值赋值给a1，然后直接用a1就行了
}