errorGroup.swift

class GroupOperation: AsyncOperation {
    let queue = OperationQueue()
    var operations: [AsyncOperation] = []
    var errors: [Error] = []
    
    override func execute() {
        print("group started")
        queue.addOperations(operations, waitUntilFinished: true)
        print("group done")
    }
  
    func finish(withError errors: [Error]) {
        self.errors += errors
    }
}