MPSCopyAllocator 无法初始化

Question

在Objective-C 我尝试使用这种方法就地编码命令缓冲区。

-(BOOL)    encodeToCommandBuffer: (nonnull id <MTLCommandBuffer>)commandBuffer  
                  inPlaceTexture: (__nonnull id <MTLTexture> __strong * __nonnull) texture  
           fallbackCopyAllocator: (nullable MPSCopyAllocator) copyAllocator  
                MPS_SWIFT_NAME(encode(commandBuffer:inPlaceTexture:fallbackCopyAllocator:));

我想创建一个新的 MPSCopyAllocator 。

我使用了文档中的以下代码。

MPSCopyAllocator myAllocator = ^id <MTLTexture> _Nonnull (MPSKernel * __nonnull filter, __nonnull id <MTLCommandBuffer> cmdBuf, __nonnull id <MTLTexture> sourceTexture)  
{  
    MTLPixelFormat format = sourceTexture.pixelFormat;  
    MTLTextureDescriptor *d = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat: format width: sourceTexture.width height: sourceTexture.height mipmapped: NO];  

    id <MTLTexture> result = [cmdBuf.device newTextureWithDescriptor: d];  

    return result;  
    /  
};

但是我在问题导航器中遇到了语义问题

Incompatible block pointer types initializing '__strong MPSCopyAllocator' (aka 'id<MTLTexture>  _Nonnull (^__strong)(MPSKernel * _Nonnull __strong, id<MTLCommandBuffer>  _Nonnull __strong, id<MTLTexture>  _Nonnull __strong)') with an expression of type 'id<MTLTexture>  _Nonnull (^)(MPSKernel * _Nonnull __strong, id<MTLCommandBuffer>  _Nonnull __strong, id<MTLTexture>  _Nonnull __strong)'

MPSCopyAllocator 定义

typedef id <MTLTexture> __nonnull NS_RETURNS_RETAINED (^MPSCopyAllocator)( MPSKernel * __nonnull filter,  
                                                                          id <MTLCommandBuffer> __nonnull commandBuffer,  
                                                                          id <MTLTexture> __nonnull sourceTexture);

创建 MPSCopyAllocator 的正确方法是什么？

Answer 1

遗憾的是，在将其分配给变量时，您需要在块定义中包含 NS_RETURNS_RETAINED：

MPSCopyAllocator allocator = ^id <MTLTexture> NS_RETURNS_RETAINED(MPSKernel *filter,
                                                                  id <MTLCommandBuffer> commandBuffer,
                                                                  id <MTLTexture> sourceTexture)
{
    // ...
};

为了简洁起见，我在这里省略了可空性注释，因为它们是可选的。

MPSCopyAllocator 无法初始化

MPSCopyAllocator can't initialize

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