在 swift3 中使用字节

Question

float *vertexBuffer = (float *)positionSource.data.bytes;

'bytes' is unavailable: use withUnsafeBytes instead

但是我不知道怎么用

_ = positionSource?.data.withUnsafeBytes({ (<#UnsafePointer<ContentType>#>) -> ResultType in

   })

Answer 1

withUnsafeBytes是泛型方法，ContentType是推断从闭包的类型。有

data.withUnsafeBytes { (vertexBuffer: UnsafePointer<Float>) in
    // Use  vertexBuffer ...
}

你会得到一个 UnsafePointer<Float> 指向数据中的字节。请注意，此指针不得在闭包之外使用。

您还可以计算结果并将其从闭包传回给来电者。示例：

let result = data.withUnsafeBytes { (vertexBuffer: UnsafePointer<Float>) -> Float in
    let result = // ... compute result ...
    return result
}

Answer 2

我想你可以这样做。

let str = "hello"
let strData = str.data(using: String.Encoding.utf8)!
strData.withUnsafeBytes { (bytes: UnsafePointer<CChar>) -> Void in
          print("\(bytes[1])")  //exp: access as c string
}

希望能帮到你！

在 swift3 中使用字节

Using bytes in swift3

unsafe-pointers

swift