tech, code & whatever...

[jeffyuhaoliu]

Big Nerd Ranch iOS Training Day 6 & 7

On Day 6 & 7, we covered a wide variety of topics. Things of note are...

Web Services - how to call it and parse things from it

NSXMLParser

NSJSONSerialization

Touch Events and how they all inherit from UIResponder

Instruments in XCode and how it can help with leaks, what lines of code is taking a long time to process and etc. 

Core Animation aka LayerKit

Core Data, this is an internal storage mechanism that you can bind to controls within iOS controls

Key Value Observing (KVO) and Key Value Coding (KVC)

Here are my notes for these 2 days.

Day 6

developer.apple.com

Sample code

Order in things arrive when starting an application

+ initialize

Don’t init super

Note: This is a class method

- init

- application: didFinishLaunchingWithOptions:

NSStringFromSelector(_cmd)

Shows the method that is currently running

You have to put this on each method you want to log

[[NSNotificationCenter defaultCenter] addObserverForName:nil object:nil queue:nil usingBlock:^(NSNotification *n) {             NSLog(@”notified! %@”, [n name]); }]

A way to look at all registered notifications on the application

Doesn’t matter where this is called, it will list out the notifications on NSLog

- (BOOL)respondsToSelector:(SEL)aSelector {             NSLog(@”Awww, someone cares! about: %@”, NSStringFromSelect(aSelector));             return [super respondsToSelector: aSelector]; }

Put this method in the app delegate, this will show all possible delegate methods that will be asked

Not sure if you need to put this in other classes, you might need to

Web Services

No DB internally in iPhone

UIWebView

You can inject JavaScript to the page!

NSXMLParser

XML Parser

libXML in C

Use this on the lower level if performance becomes an issue

According to Scott, this will eat NSXMLParser for lunch...

NSJSONSerialization

JSON Parser

Question: Why is it that in Homepwner, some properties declared in the top viewcontroller are strong and others are weak?

If you notice, weak is referenced in IBOutlet. Reason why this is the case, these outlets belong in the “Content View” (open up the .xib file in Interface Builder) and the retain count is maintained by the view controller that contains it.

Note: If ARC is turned on, it will take care of this automatically and you don’t have to worry about it.

StoryBoard

Scott: Great for prototyping and might not want to use for coding

Will be a challenge to integrate storyboard with .xib approach

Not so good working with a team

Does not scale well into a larger application

Touch Events and UIResponder

Override these…

- touchesBegan: withEvent

- touchesMoved: withEvent

- touchesEnded: withEvent

- touchesCancelled: withEvent

UIGestureRecognizer

add them to views

Note: There is a really interesting method that was written that checks the closest line to a point that is tapped on screen in Chapter 21 - Page 430.

Note: Stopped at Page: 434

Debugger

You can right click on the breakpoint and do more stuff to the spot on the breakpoint

lldb - command line for debugging

Instruments

Manage Schemes - specify what you would like to do when running the profiling tools

For more information, look at chapter 22

“Instruments User Guide” in Apple Developer if you want more information

Core Animation aka LayerKit (Chapter 23)

Instead of redrawing, it uses layers to make sure the animations are smooth

For everything view in the hierarchy, there is a backing view in the layer

It actually creates an illusion, it creates an animation presentation, but the view actually moves there directly

This is awesome, because we can animate all kinds of stuff because every view have a layer

CALayer and CAAnimation

See samples: MoveMe, Touches

Day 7

TempChat sample code

Talk about sockets

NSUserDefaults

- registerDefaults

Takes an NSDictionary with the factory defaults. These will be used if no other values have been set

Can add Settings Bundle that loads the preferences of NSUserDefaults so that your user can go to the Settings menu and change these preferences

Singleton

A method that starts with “shared” it generally means its a Singleton

Scott Ritchie:

[email protected]

[email protected]

Core Data

Not an interface to a SQL database!!! It is its own internal mini-relational database, SQLite.

Reason why you would use this is because just saving persistence as an archive file into the filesystem is its all or nothing nature: to access anything in the archive, you must unarchive the entire file. Core Data has better performance because it can fetch a small subset of the stored objects.

Persistence Framework - This is just an internal way to store objects locally

You can bind Core Data to controls in iOS, just that you can’t do it in Interface Builder for iOS, but… you can do it in Cocoa

Fetches objects from store (file)

Tracks changes made to objects

Saves changes to store (file)

Store types:

SQLite (file)

XML (file) Not on iPhone

Binary (file)

In memory

NSManagedObjectContext

Key Value Observing (KVO) and Key Value Coding (KVC)

In the view controller that “monitors” things specified (via a key path), this way, for instance, if something is changed in the HypnoTime app, you redraw something ([self setNeedsDisplay];)

[jeffyuhaoliu]

Big Nerd Ranch iOS Training Day 5

On Day 5, we covered UINavigationController, Constraints and auto-layout in Interface Builder that helps with building auto-layout iPhone templates, NSCoding which provides a basis for archiving (where objects and other structures are stored on disk) and distribution (where objects are copied to different address spaces), more detail on NSNotificationCenter, and Subclassing UITableViewCell.

Just as a side note, constraints and auto-layout was extremely confusing and complex to me. This topic requires more exploration. According to Scott Ritchie (our instructor), auto-layouts have been changed in iOS 7 and is now actually a lot better than iOS 6. Apparently, auto-layouts in iOS 6 was turned off 

Here are my notes for day 5.

UINavigationController - aka the Navigation Bar!

In iOS 7, navigation bar is translucent, which means things can now be covered by the navigation bar. To simulate that in Interface Builder, under Simulated Metrics in the Attribute Inspector in Top Bar, change the setting to Translucent Navigation Bar

Shortcut:

option + click = Opens stuff in split screen!!!

SEL

SEL data type is a pointer to a selector and that a selector is the entire message name including any colons.

NSDictionary

Constraints in Interface Builder

NSCoding

This deals with saving the stuff to the phone

- encodeWithCoder: use this when we want to save something to disk

- initWithCoder: use this when we want to grab something from disk

Simulator -

Folders

Finder -> Go -> option + Library

Path: /Users/jeffliu/Library/Application Support/iPhone Simulator/7.0/Applications

How to simulate Low Memory

Hardware -> Simulate Memory Warning

NSNotificationCenter (Page 337)

another form of callbacks

One purpose of notification center is to allow multiple objects to register a callback for the same event. Any number of objects can register as an observer for the same notification name. When the notification occurs, all of these objects are sent the message they register with (in no particular order). Thus, notifications are a good solution when more than one object is interested in an event and only one object can generate those events.

Another benefits of the notification center is that objects don’t have to have pointers to each other to send messages.

Model-View-Controller-Store

Design model for making sure things are stored when phones get put into different app stages. 

Not running

Inactive

Active

Background

Suspended

Subclassing UITableViewCell

When do views redraw themselves

setNeedsDisplay

override -layoutSubviews

[jeffyuhaoliu]

Big Nerd Ranch iOS Training Day 4

Today we mainly covered different UIView and UIViewControllers. Some of them are:

UIScrollView

UITabBarController

UITableView

Something that I didn't quite understand is Objective-C's implementation of a Singleton pattern. Apparently, this is where the static keyword for static variable comes in.

Also, as a last piece of goodie, the instructor recommends that we look at https://www.cocoacontrols.com. There are samples of people implementing cocoa controls.

Here are my notes for day 4.

View

Location - event delivers to the view that is touched

No Location - event delivers to First Responder

First Responder

Key

Motion

Ex: Shaking your phone, it means undo

UIView

Inherits from UIResponder

nextResponder

Inherits from NSObject

Consider overriding:

+ alloc

- init

- description

Frame is a description of where it is in the superview; relative to the superview

Bounds - will calculate what needs to be redrawn

Programming with Quartz 2D and PDF Graphics in Mac OS X - David Gelphman and Bunny Laden

Talks about drawing 2D graphics in Mac OS X,

Sprite Kit - Higher level 2D drawing mechanism that uses Quartz in the lower level

BreakPoint Navigator

You can add in “Exception Breakpoint”, so when it fails, it will breakpoint it and you can see the stack trace

UIScrollView

UIWindow

UIViewController

Apple wants you to add a view controller to UIWindow

Lazy load of views

setup to load the view and unload the view

You can override your own loadView method

if you don’t override it, it will load for .nib file in the package with the same name as the view controller

UITabBarController

Contains other view controllers

Ex: @[smtViewController,smt2ViewController]

If you subclass it, you should override

- initWIthNibName: Bundle:

- loadView

If you override it, then you tell it what to load

If you don’t… then it will look for the .nib (.xib) file

- viewDidLoad

UITableView

Use if the view does not fill the whole screen

UITableViewController

Use if you want it to fill the whole screen

UITableView have an Editing Mode

Sample controls you can get on the web

https://www.cocoacontrols.com

http://www.scoop.it/t/ios-os-x-stuff

Singleton

[jeffyuhaoliu]

Big Nerd Ranch iOS Training Day 3

Book: Vol. 1 iOS Programming Instructor by Scott Ritchie

Today we mainly covered three topics. We learned how to use the Interface Builder, putting elements on to it and etc. On the topic of Interface Builder, we also learned how to "ctrl + drag" elements in .xib files to and from the File Owner, setting up Outlets and Delegates.

We then moved on to how Objective-C would work without ARC. We learned that most of the time if we see an alloc, we basically would need to either release or autorelease. On a side note, this topic was by far the most confusing of them all.

The third topic we covered was how to work with Core Location and MapKit APIs. We created an app which found our current location and allowed us to put an annotation on the mapview.

Lastly, I learned today that you do not need a pointer to a struct. An example of this would be CLLocationCoordinate2D.

MVC - Model, View, Controller

Views - things you can see in the App

Views can be nested and can be a part of a hierarchy

Ex: UIButton

Controller - knows how to build and setup the view

Would probably not want to have lots of initializers

Model -

Would probably want lots of initializers

main.m

Contains a run loop

Stay the heck out of here

.xib files

XML Interface Builder

Shortcut

cmd + option + (1-4) - switch between attribute inspector

Interface Builder

“Files Owner” in .xib file

“ctrl + drag” = message from view controller to specific view (ex: UIButton)

“ctrl + drag” the way the message goes on runtime

IBAction - tells the interface builder this is a action that is available in the view controller

Target/Action: Target: whatever you drag to, Action: whatever you drag to

dot - is already implemented

dash - is implemented by someone else

IBOutlet - telling the .xib loading system to set value to something in the view

Connection Inspector - inspect the “Files Owner” to see all the connections or right click on the “Files Owner”

Initializers

***Important*** Page: 17 - Suggestions/Rules in iOS Programming Training Slides

A class can have zero or more initializers

One initializer is deemed “Designated”

All initializers call designated initializer

Designated initializer calls superclass’s designated initializer

Must override superclass’s designated initializer

More info: Chapter 2 (Page: 31) - Initializers in iOS Programming

Designated initializers

There is only 1 designated initializer in the class!!!

there is no way in Objective-C to tell ppl about what is the designated initializer

have “super” in it

Other initializers

they call the designated initializer with “self”

Without ARC:

Always turn on ARC! But… if you don’t turn it on below is what you need…

Note: You can turn off ARC on the file level

Without ARC, its all about pattern matching

- retain

Ups the retain count by 1

- release

Lowers the retain count by 1

- autorelease

Lower the retain count by 1… later

- dealloc

Cannot call this directly, call - release

only do stuff if you see one of the following within the same class:

new

alloc

retain

copy

Build -> Analyze to look at potential memory leaks

Core Location Delegation

Page 29 in iOS Programming Training Slides

Delegates and Protocol

CLLocationManager

setDistanceFilter

setDesiredAccuracy - the more accurate, the longer it will take to locate

setDelegate

startUpdatingLocation - this is non-blocking

CLLocation

In XCode, you can simulate the different locations

“#import” & “@import”

MapKit

First Responder

The keyboard, TextInputTrait

Happens in “TextInput” and “TextField”

[jeffyuhaoliu]

Big Nerd Ranch iOS Training Day 2

Book: Objective-C Programming Big Nerd Ranch Guide 2nd Edition by Aaron Hillegass & Mikey Ward

We went through Chapters 22 to 28 of the book today. One thing of note that is interesting and very very useful in the coming days are Callbacks. A quick summary of the three types of Callbacks in Objective-C are:

Target/Action

Delegation

Notification

My co-worker Brandon and I had a discussion about this topic and might be quite interested in this...

We also talked about the difference between mutable and immutable objects. Immutable objects cannot be changed once they are declared. Due to the way Objective-C handles memory deallocation (or garbage collection in other language), immutable objects references other objects therefore have a less memory footprint compared to mutable objects.  

Additionally, when we run the code, we can bring up the Profiler (which runs in Instruments) in Xcode. The Profiler can tell us if we have objects that have not been deallocated by ARC (aka memory leaks).

Lastly, Objective-C have a notion of Blocks. Chapter 28 covers this topic extensively. But, a quick summary is that blocks is similar to anonymous functions. 

Below are notes I took for the 2nd day.

Question: What is “copy” on page 143 for… “@property (nonatomic, copy) NSArray *assets;”?

“copy” is recommended to be used for NSString, or things that have mutable subclasses

copy is like strong, but copy makes a copy of the object

For immutable objects, it just ups the reference count

strong reference it just increments the reference count

*** For classes that have mutable subclasses… recommended to use “copy” ***

@synthesize - creates the getter and setter and the local variable for @property

Note: we no longer have to call this because Apple is now automatically creating this for us when we create property (@property)

@interface - description of the class, think of it like public in JAVA

ARC sometimes cannot deallocate when a child object references a parent element

Class Extension - extends the class in the implementation file (.m file), this way things you don’t want exposed is not exposed in the header file (.h file)

Note: Whatever you put in the class extension is “private” (Note: nothing is private in Objective-C, just the compiler doesn’t know about it because it is not in the header file)

Shortcuts:

ctrl + i - indents stuff correctly

cmd + [space] - opens up spotlight search

Instruments -> Profiler

Chapter 23… talks about strong vs weak; they relate to retain cycles

This chapter talks about how we can deal with memory leaks

Filtering & Sorting Arrays

NSMutableArray:

method: sortUsingDescriptors

method: filterUsingPredicate

NSAarray

method: filteredArrayUsingPredicate

NSPredicate

Sets collections with no order and objects can be presented only once. Useful when dealing with membership issues -- is the object in there?

NSSet / NSMutableSet

Unordered

Dictionaries are an extremely useful collection type. There are unordered and associate a key with a value. The key can be any object that is copiable and unique within the collection. Typically, they are constant strings.

NSDictionary / NSMutableDictionary

Unordered

Numbers object

NSNumber

Cannot do arithmetic calculations; use primitive type to do this

NSValue

Use this to put point, ranges, etc. in a collection

NSNull

An collection cannot have a “hole” or nil. Use this object to put into a collection

Immutable collection conserves memeory and improves performance because that collection never needs to be copied. With a mutable object, there is the possibility that some other code might change the object behind your back while you are in the middle of using it. To avoid this situation, you would have to make a private copy of the collection. And so would everyone else, which leads to multiple copies of a potentially large object.

#pragma mark

Helps with categorizing the code and ignored by the compiler

Callbacks

Target Action

Most common

Helper pattern aka Delegation

Protocol???

Only 1 delegate at a time

Notifications

aka Notification Center

There are some duplication between this and delegation

Not cross thread!!! IT WILL BLOCK!

How does Apple decide which one to use in any particular situation?

Objects that do just one thing (like NSTimer) use target-action.

Objects that have more complicated lives (like an NSURLConnection) use helper objects, and the most common type of helper object is delegate.

Objects that might need to trigger callbacks in server other objects (like NSTimeZone) use notifications.

Blocks

Same as “anonymous functions”

To the left of (^) is the return

You can assign a block to a variable

[jeffyuhaoliu]

Big Nerd Ranch iOS Training Day 1

Instructor: Scott Richie - [email protected]

Book: Objective-C Programming Big Nerd Ranch Guide 2nd Edition by Aaron Hillegass & Mikey Ward

We went through Chapters 1 to 21. For exercises related to these chapters, please visit https://github.com/jeffyuhaoliu/Big-Nerd-Ranch---iOS. 

Below are some notes I took for the 1st day.

Scott Richie - [email protected]

Shortcuts

cmd + option + click - opens application and hides all others

cmd + 1 to 8 - cylcles through tabs in navigator within XCode

cmd + ctrl + [up arrow] - will toggle between interface & implementation file

* denotes a pointer

Mutable Object - can change the object

Immutable Object is an object whose state cannot be modified after it is created

Capital letters are used for typedef and class

Lower case letter for methods, properties and etc

Objective-C does not have any namespaces!

Class methods:

+: method needs to be sent to a class

-: method needs to be sent to an instance of a class

Multiple Arguments

[obj setCount: 13];  // @selector(setCount:)

Overloads: THERE ARE NO OVERLOADS!!!

Returns: if you want a undefined return, return…

id obj;

Method Description: To get the description, hold down option

nil:

CoolClass *obj = nil; [obj doSomething]; // Nothing happens -- no error

In Objective-C, it will not blow up, it will just return 0 or nil

ARC:

objects deallocate themselves when the retain count is set to 0

Under “Build Settings”  -> “Objective-C Automatic Reference Counting”

NSString:

NSString are immutable.

Ex: NSString *myStr = @”Hello Obj students”;

Ex: NSString *emptyStr = [[NSString alloc] init];

Ex: NSString *emptyStr = [NSString stringWithFormat:@”I love the number %d”, 7];

if (moon == cheese) {       // You will never get here! Pointer comparison! }

if ([moon isEqualToString:cheese]) {       // You may get here one day... }

NSUInteger:

Is not a class… it is actually a typedef of unsigned long

NSArray:

It is immutable

Everything that you put in there has to be a class

NSMutableArray

for (NSUInteger i=0; i<[listOfStuff count]; i++) {       NSLog(@”Item at index %d is %@”, i, [listOfStuff objectAtIndex:1];       id item = [list objectAtIndex:i]; }

for (id item in list) {       // Do something with item... }

Class:

Methods:

All methods are public

Instance Variables:

@private, @public, @protected

However, Apple doesn’t care about that as much now, they care more about stuff in the header files

Accessor methods:

Setter methods

Getter methods

Note: In Objective-C, do not use “get” in the property name because it means something different in Objective-C

Properties:

Underscore: denotes the local variable used for the getter and setting. HOWEVER! do not directly access the getter and setter local variables.

Dot-Notation: It is actually a shortcut, when using dot notation with an object, a message is being sent and not accessing the property directly.

Benefit: Helps avoid calling the local variables directly

atomic vs nonatomic - related to threads

atomic - This means that the synthesized accessors ensure that a value is always fully retrieved by the getter method or fully set via the setter method, even if the accessors are called simultaneously from different threads.

atomic is the default

You can use the nonatomic property attribute to specify that synthesized accessors simply set or return a value directly, with no guarantees about what happens if that same value is accessed simultaneously from different threads.

Almost always will use nonatomic

self:

equivalent to “this”

Instance Variables

Reference Types: Specify behavior how ARC deallocate objects

strong - This is default

weak - This is very unusual

@class

#import-ing a header file “pastes” the content

If possible, it is more efficient to use @class

[jeffyuhaoliu]

Where was Sandboxr when we were kids? Instead of dragging our parents around on a hunt for the perfect figurine, we could have used the company's new web app to easily manipulate a virtual model and get a 3D printed statuette in the exact pose we wanted. There's compensation for the lost opportunities of our childhood, however. The creation tool allows for customized accessories, scenes and sizing, and it's expected to have reasonable prices of about $12 for a 2.5-inch character and over $20 for a 3.5-inch version. The best news may simply be the likelihood of a figurine existing in the first place -- Sandboxr sees itself as a platform for everyone from 3D animators through to game developers and dedicated toy companies, many of which can use existing 3D models to start a collectible line. The printing service is currently invitation-only and plans a Kickstarter fundraising drive to scale larger, but it's easy to see an end to the days of limited edition figurines -- much to the delight of our inner child.