Table of contents
Section 2: Fundation Framework
Section 3: Enhancements of NSLog relative to print
Section 5: New data types in oc
Section 6: Classes and Objects
Class method declaration and implementation
Section 7: Storage of classes and objects
Section 9: Group navigation mark #pragma mark
Section 10: The difference between methods and functions
Section 11: Convenient way to add files
Section 12: Objects and Methods
Section 13: Exception Handling
Section 14: Object methods and class methods
Section 17: Attribute setters and getters
Section 18: Relationships between objects
Section 19: Static variables in OC
Characteristics of inheritance
Section 23: Richter Substitution Principle
Twenty-five: How does the subclass find the parent class and how to store it?
Section 26: The nature of classes
Section 30: @sysnthesize keyword
Chapter 31: Improvements to @property
Property parameters of @property
Section 32: Static type, dynamic type
Section 36: responseToSelector, isKindOfClass, isMemberOfClass, isSubclassOfClass
Section 40: Autorelease pool @autoreleasepool
Section 42: Specify which class uses MRC
Section 46: Commonly used methods in the Fundation library
Reading and writing strings to files
Chapter 51: NSDictionary dictionary array
Section 52: NSMutableDictionary
Section 1: Introduction to OC
Section 2: Fundation Framework
Section 3: Enhancements of NSLog relative to print
Section 4: NSString
Section 5: New data types in oc
Section 6: Classes and Objects
Class method declaration and implementation
Section 7: Storage of classes and objects
Because the method is universal
Section 8: nil and NULL
Section 9: Group navigation mark #pragma mark
Section 10: The difference between methods and functions
Section 11: Convenient way to add files
Section 12: Objects and Methods
Section 13: Exception Handling
Section 14: Object methods and class methods
Section 15: NSString
Section 16: Anonymous Objects
Section 17: Attribute setters and getters
Section 18: Relationships between objects 
Section 19: Static variables in OC
Section 20: self
The following two sentences have the same meaning, both represent the name attribute of the current object
Chapter 21: Inheritance
Characteristics of inheritance
Section 22: Access modifiers
Section 23: Richter Substitution Principle
Section 24: description
Similar to c#'s tostring()
Twenty-five: How does the subclass find the parent class and how to store it?
Section 26: The nature of classes
Section 27: SEL(selector)
Section 28: Point Grammar
That is, if there is no corresponding setter method, an error will be reported.
Section 29: @property keyword
Section 30: @sysnthesize keyword
Section 31: Improvements to @property
The automatically generated attribute is _attribute name, which is underlined.
Property parameters of @property
MRC
Section 32: Static type, dynamic type
Section 34: NSObject, id type
Section 35: instanceType
Section 36: responseToSelector, isKindOfClass, isMemberOfClass, isSubclassOfClass 
Section 37: init
Custom construction method
Section 38: Memory Management
Reference counter
MRC 、ARC
wild pointer
Section 39: @class
Section 40: Autorelease pool @autoreleasepool
Chapter 41: ARC
Recycling refers to recycling objects, which is the object [person new]
Circular references under ARC
Summarize
Section 42: Specify which class uses MRC
Section 42: Classification
Compilation order
informal agreement
Section 43: Extension
Similar to interface
Section 44: block type
Abbreviation for Block
Define it in the parameters of the function, take out the name of the Block and put it outside
Section 45: Protocol
C#-like interface
Section 46: Commonly used methods in the Fundation library
NSString
Reading and writing strings to files
NSURL reads and writes files
String comparison
Generally, compare pictures with serial numbers.
Find substring
Search
NSRange from back to front
String interception
String replacement
Conversions to other types
Remove lowercase letters from the beginning and the end, uppercase letters from the beginning and the end, and specified letters from the beginning and the end.
Section 47: NSMutableString
Section 48: NSArray
Use @ to print out all elements of NSArray
Traverse
Write files, read files
String related methods
Section 49: NSMutableArray
Section 50: NSNumber
Chapter 51: NSDictionary dictionary array
Value:
dic[@"key"]
dic object for key:@"key"
If the value is not available, return nil
[dic allkeys] 、 [dic allvalues]
Traverse:
Storage principle:
Each key passes the hash algorithm to obtain the subscript and save it.
Section 52: NSMutableDictionary
Write and read files
Storage principle
Section 53: NSFileManager
Files starting with dot are hidden files and can be printed by ls-al
Create, copy, delete files
CGPoint、CGSize、CGRect
NSValue
NSDate
It will be automatically converted to the system time zone during conversion.
NSCalender: Calendar object
Chapter 54: copy
Section 55: Singleton Pattern
