Swift to swift 2 守卫让

Question

let renderEncoderOpt = commandBuffer.renderCommandEncoderWithDescriptor(renderPassDescriptor)

if let renderEncoder = renderEncoderOpt {
  renderEncoder.setRenderPipelineState(pipelineState)
  renderEncoder.setVertexBuffer(vertexBuffer, offset: 0, atIndex: 0)
  renderEncoder.drawPrimitives(.Triangle, vertexStart: 0, vertexCount: 3, instanceCount: 1)
  renderEncoder.endEncoding()
}

上面的代码抛出一个

 Initializer for conditional binding must have Optional type, not 'MTLRenderCommandEncoder'

如果我尝试将 renderEncoderOpt 设为可选，问题仍然存在。我已经尝试使用 guard let 与 if let 进行测试，并尝试将其设置为可选项，并重新声明类型等，但它一直回到这个问题。这在 swift 1/1.2 中工作正常

有人指点吗？

Answer 1

renderCommandEncoderWithDescriptor 不返回可选值，因此您应该完全删除 if let 条件绑定(bind)，直接使用结果。

let renderEncoder = commandBuffer.renderCommandEncoderWithDescriptor(renderPassDescriptor)

renderEncoder.setRenderPipelineState(pipelineState)
renderEncoder.setVertexBuffer(vertexBuffer, offset: 0, atIndex: 0)
renderEncoder.drawPrimitives(.Triangle, vertexStart: 0, vertexCount: 3, instanceCount: 1)
renderEncoder.endEncoding()