Transparent Unity background on ios with unity 5.2

HI all:
I want unity scene with transparent background,so that my native view could show behind the unity scene.I found some resolution in version 4.2,but not work in 5.2.
The unity scene background always black after set camera color with (0.0,0.0,0.0,0.0) and surface->layer.opaque = NO.
I am a newer for unity. So if anyone knows a solution for this issue or has some idea please let me know. Thanks !

On iOS with Metal API you have to change the file to:

CGFloat backgroundColor = {0,0,0,0};

and add

surface->layer.opaque = NO;

Works for me on Uniti 5.2.