Open Radar

 
Marked as duplicate of 18272350

Summary:
Attempting to use a QOS class as an argument to the GCD function `dispatch_get_global_queue` in the Swift language fails with the reason "error: 'qos_class_t' is not convertible to 'Int'". It appears that unlike `dispatch_queue_attr_make_with_qos_class` which explicitly requires a dispatch_qos_class_t (a typealiased qos_class_t) argument, `dispatch_get_global_queue`'s signature accepts an Int so that it's compatible with the older dispatch_queue_priority_t values. In this case it means that it's not possible to use quality of service values as is recommended[1] by the documentation.

[1]: "It is recommended to use quality of service class values to identify the well-known global concurrent queues."

Steps to Reproduce:
1. Install Xcode 6 Beta 4
2. Create a new OS X playground (note that this issue occurs on both platforms, but for the sake of example...)
3. Enter the code `let queue = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)`
4. Observe warning

Expected Results:
I would expect `dispatch_get_global_queue` to accept both the older dispatch queue priorities and newer QOS classes.

Actual Results:
An error occurs

Version:
Version 6.0 (6A267n)
Version 10.10 (14A298i)

Notes:


Configuration:
Always occurs running Xcode 6 Beta 4 in Yosemite 10.10 Beta 4