Visual Programming MCQs with Answers
Practice important Visual Programming MCQs with answers and explanations.
Multiple Choice Questions
Q791: How do you call a block asynchronously on the main queue?
- A: dispatch_sync(mainQueue, block)
- B: dispatch_async(mainQueue, block)
- C: dispatch_block(mainQueue, block)
- D: dispatch_run(mainQueue, block)
View Answer
B
Q792: What is the purpose of the canBecomeFirstResponder method?
- A: To check if the view can become the first responder
- B: To make the view the first responder
- C: To handle touch events
- D: To set the background color of the view
View Answer
B
Q793: What does the motionBegan:withEvent: method do in iOS?
- A: Handles the beginning of a motion event like shaking
- B: Starts a new thread for calculations
- C: Initializes touch events
- D: Handles the end of a motion event
View Answer
A
Q794: What is the role of blocks in Objective-C?
- A: To manage memory more efficiently
- B: To capture variables and define inline functions
- C: To replace all method calls with function pointers
- D: To handle UI updates synchronously
View Answer
B
Q795: How does dispatch_get_global_queue differ from dispatch_get_main_queue?
- A: dispatch_get_global_queue returns a global queue for background tasks, while dispatch_get_main_queue is for UI updates
- B: dispatch_get_global_queue returns a queue for UI updates, while dispatch_get_main_queue is for background tasks
- C: dispatch_get_global_queue creates a new thread, while dispatch_get_main_queue manages existing threads
- D: dispatch_get_global_queue and dispatch_get_main_queue are the same functions with different names
View Answer
A
Q796: What is the purpose of dispatch_async in the context of image downloading?
- A: To perform the task on the main thread
- B: To execute a block asynchronously on a specified queue
- C: To synchronize tasks across multiple queues
- D: To cancel a block's execution
View Answer
B
Q797: In the given code, how is the image data downloaded?
- A: Using dispatch_sync to perform the download task
- B: By creating a new thread to handle the download
- C: Using dispatch_async to handle the download asynchronously
- D: By calling a method to directly download the image
View Answer
A
Q798: What does the dispatch_sync function do in the provided code?
- A: Executes a block asynchronously
- B: Executes a block synchronously on the specified queue
- C: Delays the execution of a block on the main thread
- D: Cancels the execution of a block on a specified queue
View Answer
B
Q799: Where should the image be displayed after it has been downloaded in the provided code?
- A: Directly in the main queue after downloading
- B: On a secondary thread to avoid blocking the main thread
- C: On the main queue to ensure it is displayed correctly in the UI
- D: In the background while the user interacts with other elements
View Answer
C
Q800: What does the fileLocation method do?
- A: Returns the URL of the image file
- B: Returns the path to the document directory with the filename appended
- C: Returns the path to the temporary directory with the filename appended
- D: Returns the URL of the file on the web
View Answer
B