Visual Programming MCQs with Answers
Practice important Visual Programming MCQs with answers and explanations.
Chapter: 44
Q781:
What does the touchesMoved:withEvent: method handle in touch events?
A. Initial touch event
B. Finger moving across the screen
C. Touch removal from the screen
D. System interruption during touch
Correct Answer:
B
Chapter: 44
Q782:
How do you handle a double tap in a touch event?
A. Call [self clearAll]
B. Call [self setNeedsDisplay]
C. Call [self endTouches:]
D. Call [self startUpdatingLocation]
Correct Answer:
A
Chapter: 44
Q783:
What class is used to represent a line in the drawing app?
A. CGPoint
B. UIView
C. Line
D. UIColor
Correct Answer:
C
Chapter: 44
Q784:
How do you clear all lines from the drawing view?
A. Call [linesInProcess removeAllObjects] and [completeLines removeAllObjects]
B. Call [self setNeedsDisplay]
C. Call [self clearAll]
D. Call [self drawRect:]
Correct Answer:
C
Chapter: 44
Q785:
In the drawRect: method, how are complete lines drawn?
A. Set color to red and iterate through linesInProcess
B. Set color to black and iterate through completeLines
C. Set color to blue and iterate through linesInProcess
D. Set color to green and iterate through completeLines
Correct Answer:
B
Chapter: 44
Q786:
What does the transformLineColorsWithBlock: method do?
A. Transforms line colors using a block
B. Clears all lines from the view
C. Updates the line endpoints based on touch movements
D. Draws all lines in the completeLines array
Correct Answer:
A
Chapter: 44
Q787:
How is color calculated based on the line's angle and length?
A. Using transformLineColorsWithBlock: with a predefined block
B. Using drawRect: method to set color for each line
C. Using colorize method with a block for calculating colors
D. Using clearAll method to reset colors
Correct Answer:
C
Chapter: 44
Q788:
Which method is called to start a new thread in the DidFinishLaunchingWithOptions: method?
A. [NSThread detachNewThreadSelector:toTarget:withObject:]
B. [NSThread start]
C. [NSThread run]
D. [NSThread create]
Correct Answer:
A
Chapter: 44
Q789:
How does Grand Central Dispatch manage concurrent tasks?
A. By creating new threads for each task
B. By using dispatch queues to manage pools of threads
C. By manually managing thread synchronization
D. By running tasks on the main thread only
Correct Answer:
B
Chapter: 44
Q790:
What does the dispatch_sync function do in GCD?
A. Executes a block asynchronously on a specified queue
B. Executes a block synchronously on a specified queue
C. Delays the execution of a block on the main thread
D. Cancels the execution of a block on a specified queue
Correct Answer:
B
Chapter: 44
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)
Correct Answer:
B
Chapter: 44
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
Correct Answer:
B
Chapter: 44
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
Correct Answer:
A
Chapter: 44
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
Correct Answer:
B
Chapter: 44
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
Correct Answer:
A
Chapter: 45
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
Correct Answer:
B
Chapter: 45
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
Correct Answer:
A
Chapter: 45
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
Correct Answer:
B
Chapter: 45
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
Correct Answer:
C
Chapter: 45
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
Correct Answer:
B