Mike Thongvanh mthongvanh

Okay, let's draw a parallel between the Liskov Substitution Principle (LSP) and finance. It’s about ensuring that if you can replace a base class object with one of its subclasses without changing the code that uses it, your system remains stable and predictable.

The Core Idea of LSP:

LSP states that if a subclass should be able to replace its parent class in any context, it must behave identically to the base class in all relevant situations. This means that if you have a function expecting an Account object, it should work equally well with a SavingsAccount or a CheckingAccount (assuming they both inherit from the Account class).

The Financial Analogy: Investment Accounts

Let's use the concept of investment accounts as our financial analogy.

	{
	"agendaFilters": [{
	"id": 1,
	"display": "Conferences",
	"value": "conferences",
	"valueType": "decisionTree",
	"filterType": "",
	"options": [{
	"id": 1,
	"display": "Ellucian Live",

	Debug Log Statement
	----------------------
	DLog(@"\n<#debugging message#> <#%@#>",<#args#>);

	NSString Convenience Method
	----------------------------
	[NSString stringWithFormat:@"<#%@#>",<#args#>]

	Dispatch Asynchronously on Main Queue
	-------------------------------------

	// In both versions, we're feeding a string to the NSFileManager method, but only the second one succeeds. In the debugger console, they both appeared with the file:// so it was a bit difficult to debug. Of course, I'd momentarily forgot about every. other. time. it has happened.

	// Version 1
	- (BOOL)fileExistsInCaches:(NSString *)filename
	{
	NSString *path = [NSString stringWithFormat:@"%@%@",[self cacheDirectory],filename];
	// path = file://Users/mthongvanh/etc/etc/etc
	return [[NSFileManager defaultManager] fileExistsAtPath:path];
	}

	#import "DynamicScrollviewResizingViewController.h"

	@interface DynamicScrollviewResizingViewController ()
	@property (weak, nonatomic) IBOutlet UILabel *dynamicLabel;
	@end

	@implementation DynamicScrollviewResizingViewController

	- (void)viewDidLoad {
	[super viewDidLoad];

	enum PersonDescription {
	case Singular, Dual, Plural

	struct Portrayal {
	var literal: String, numeral: Int
	}

	var portrayal: Portrayal {
	switch self {
	case .Singular:

	- (void)willTransitionToTraitCollection:(UITraitCollection *)newCollection withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
	[super willTransitionToTraitCollection:newCollection withTransitionCoordinator:coordinator];

	NSLog(@"nav size %@", NSStringFromCGRect(self.navigationController.navigationBar.bounds));
	}

	// Problem: AVAudioRecorder failed to initialize by crashing on initialization method
	// Diagnosis: NSURL *audioURL was nil at audioRecorder initiliazation point because audioURL's weak declaration
	// Solution: Declare NSURL *audioURL as strong to ensure it does not get deallocated prematurelys.
	// *Side note suggestion: Be sure to use [AVAudioRecorder record] instead of prepareToRecord since record will call it implicitly
	// and handle errors appropriately!

	// properties
	// @property (weak, nonatomic) NSURL audioURL; / User's original declaration */
	@property (strong, nonatomic) NSURL *audioURL;
	@property (strong, nonatomic) AVAudioRecorder *audioRecorder;

	// Intent: Create a 7-Column collection view where the first and last column are wider than the middle columns
	// Solution: Via the UICollectionViewDeleateFlowLayout calculate the correct size of the cells

	const NSUInteger daysInWeek = 7;
	const CGFloat cellHeight = 54.f;
	const CGFloat sizeRatioForWeekStartEnd = 0.20;
	const CGFloat sizeRatioForMiddleDays = (1 - (2 * sizeRatioForWeekStartEnd)) / (daysInWeek - 2);

	- (CGSize)collectionView:(UICollectionView )collectionView layout:(UICollectionViewLayout )collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
	CGSize cellSize = CGSizeZero;

	// Problem: Collection View data does not appear after calling [UICollectionView reloadData] in [PFQuery findObjectsInBackgroundBlock:]
	// Symptoms: The correct number returns in numberOfItems: but cellForItem: is never called
	// Solution: Try performing collection view updates manually via performBatchUpdates: or reloadItemsAtIndexPaths: or reloadSectionsAtIndexSet:

	- (void)queryForPhoto {
	NSLog(@"%s", __PRETTY_FUNCTION__);

	PFQuery *query = [PFQuery queryWithClassName:@"Image"];
	PFUser *user = [PFUser currentUser];
	[query whereKey:@"user" equalTo:user];