2019-09-27swift内嵌函数内存安全

一：内嵌函数引用inout的参数时不能是逃逸的

func func1(inoutPara para : inout Int) {       

para = 3   

    func nestFun() ->  () -> Int{                                  

        return { 

            return para + 1

        }   

    }   

    nestFun() 

}

编译器会报错：Escaping closure captures 'inout' parameter 'para'

二：如果不对inout参数进行修改，可以采用这种形式解决:

 func nestFun() ->  () -> Int{            

        para = 4                     

        return {

            [para] in

            return para + 1

        }    

    }    

如果对inout参数进行修改，可以采用复制inout参数修改后再赋值给inout参数这种形式解决:

func func2(queue:DispatchQueue,inoutPara para :inoutInt) {

   var localX = para

    defer{ para = localX }

    // Operate on localX asynchronously, then wait before returning.

    queue.async { someMutatingOperation(&localX) }

    queue.sync{}

}

详细文档 Memory Safety.

三：func中不可再操作inout的原变量

var para=5

func inoutfunc(inoutpara :inoutInt) {

    print(inoutpara)

    print(para)

}

inoutfunc(inoutpara: &para)

报错：error: Execution was interrupted,reason: signal SIGABRT.

The process has been left at the point where it was interrupted,use "thread return -x" to return to the state before expression evaluation.

上例中，不可使用print（para）语句