本文介绍了将Objective-C方法转换为Swift for NSInputStream(将字节转换为double)的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我在Objective-C中有以下代码:

I have the following code in Objective-C:

- (double)readDouble
{
    double value = 0.0;

    if ([self read:(uint8_t *)&value maxLength:8] != 8)
    {
        NSLog(@"***** Couldn't read double");
    }

    return value;
}

它有效。但我不知道如何将其转换为Swift。这是我的代码:

It works. But I don't know how to convert it to Swift. Here is my code:

public func readDouble() -> Double {

    var value : Double = 0.0

    var num = self.read((uint8_t *)&value, maxLength:8) // got compiling error here!
    if num != 8 {

    }
}

错误信息是:

有人可以帮忙吗?谢谢

我正在使用的测试数据(1.25):

The testing data I'm using (1.25):

14 AE 47 E1 7A 14 F4 3F

更新:

一个简单的c解决方案,但是如何在Swift中执行此操作?

A simple c solution, but how to do this in Swift?

double d = 0;
unsigned char buf[sizeof d] = {0};

memcpy(&d, buf, sizeof d);


推荐答案

这应该有效:

let num = withUnsafeMutablePointer(&value) {
    self.read(UnsafeMutablePointer($0), maxLength: sizeofValue(value))
}

解释 withUnsafeMutablePointer()使用设置为地址的唯一参数
$ 0 ,以简写表示法)调用闭包(块)值

Explanation: withUnsafeMutablePointer() calls the closure (block) with the only argument($0 in shorthand notation) set to the address of value.

$ 0 的类型为 UnsafeMutablePointer< Double> read()期望
UnsafeMutablePointer< UInt8> 作为第一个参数,因此另一个转换
是必要的。然后将闭包的返回值分配给 num

$0 has the type UnsafeMutablePointer<Double> and read() expects anUnsafeMutablePointer<UInt8> as the first argument, therefore another conversionis necessary. The return value of the closure is then assigned to num.

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07-31 10:34