Custom Singleton for iOS development: custom for iOS development

Custom Singleton for iOS development: custom for iOS development

Custom Singleton for iOS development

Here I use macros:

//. H
# Define single_interface (class) + (class *) shared # class;

//. M
// \ Indicates that the next row also belongs to a macro.
// ## It is a separator

• # Define single_implementation (class )\
• Static class * _ instance ;\
• \
• + (Class *) shared # class \
• {\
• If (_ instance = nil ){\
• _ Instance = [[self alloc] init]; \
• }\
• Return _ instance ;\
• }\
• \
• + (Id) allocWithZone :( NSZone *) zone \
• {\
• Static dispatch_once_t onceToken ;\
• Dispatch_once (& onceToken, ^ {\
• _ Instance = [super allocWithZone: zone]; \
• });\
• Return _ instance ;\
• }

Of course, there are other more comprehensive methods, but the principle of the above is the same, the practical use of the above can be used at ordinary times.
// The Singleton mode varies in the ARC \ MRC environment. You need to write two sets of different codes.
# If _ has_feature (objc_arc)
// ARC

// Override allocWithZone: method. Create a unique instance here (pay attention to thread security)

• + (Id) allocWithZone :( struct _ NSZone *) zone
• {
• @ Synchronized (self ){
• If (! _ Instance ){
• _ Instance = [super allocWithZone: zone];
• }
• }
• Return _ instance;
• }
• // Provides a class method to allow external access to a unique instance
• + (Instancetype) specified instance
• {
• @ Synchronized (self ){
• If (! _ Instance ){
• _ Instance = [[self alloc] init];
• }
• }
• Return _ instance;
• }
• // Implement copyWithZone: Method
• + (Id) copyWithZone :( struct _ NSZone *) zone
• {
• Return _ instance;
• }

# Else
// Non-ARC

// Non-ARC (MRC), single-instance mode implementation (several more steps than ARC)


// Override allocWithZone: method. Create a unique instance here (pay attention to thread security)

• + (Id) allocWithZone :( struct _ NSZone *) zone
• {@ Synchronized (self ){
• If (! _ Instance ){
• _ Instance = [super allocWithZone: zone];
• }
• }
• Return _ instance;
• }
• // Provides a class method to allow external access to a unique instance
• + (Instancetype) specified instance
• {
• @ Synchronized (self ){
• If (! _ Instance ){
• _ Instance = [[self alloc] init];
• }
• }
• Return _ instance;
• }
• // Implement copyWithZone: Method
• + (Id) copyWithZone :( struct _ NSZone *) zone
• {
• Return _ instance;
• }
• // Memory Management Method
• -(Id) retain
• {
• Return self;
• }
• -(NSUInteger) retainCount
• {
• Return 1;
• }
•  
• -(Oneway void) release
• {
• }
•  
• -(Id) autorelease
• {
• Return self;
• }

# Endif