ios - 'init' 不可用 :use 'withMemoryRebound(to:capacity:_)' to temporarily view memory as another layout-compatible type

Question

这是一个错误:

'init' is unavailable:use 'withMemoryRebound(to:capacity:_)' to temporarily view memory as another layout-compatible type.

这是我的代码:

var inputSignal:[Float] = Array(repeating: 0.0, count: 512)

let xAsComplex = UnsafePointer<DSPComplex>( inputSignal.withUnsafeBufferPointer { $0.baseAddress } )//error here

为什么？如何解决？

Answer 1

首先，不推荐使用成语.withUnsafeBufferPointer { $0.baseAddress } 来获取Swift Array 的地址。不能保证从该习语中获取的地址在闭包之外有效。

所以，你可以这样写:

inputSignal.withUnsafeBufferPointer {buffer in
    buffer.baseAddress!.withMemoryRebound(to: DSPComplex.self, capacity: inputSignal.count / (MemoryLayout<DSPComplex>.size/MemoryLayout<Float>.size)) {xAsComplex in
        //`xAsComlex` is guaranteed to be valid only in this closure.
        //...
    }
}

如果您需要使用稳定指针，您可能需要将它们作为实际指针进行管理。

let inputSignalCount = 512
let inputSignal = UnsafeMutablePointer<Float>.allocate(capacity: inputSignalCount)
inputSignal.initialize(to: 0.0, count: inputSignalCount)

//...

inputSignal.withMemoryRebound(to: DSPComplex.self, capacity: inputSignalCount / (MemoryLayout<DSPComplex>.size/MemoryLayout<Float>.size)) {xAsComplex in
    //`xAsComlex` is guaranteed to be valid only in this closure.
    //...
}

//...

//Later when `inputSignal` is not needed any more...
inputSignal.deinitialize(count: inputSignalCount)
inputSignal.deallocate(capacity: inputSignalCount)