Medium/UISheetPresentationController/2.m

UISheetPresentationController_2.m

//
// SAPatternReference
//

@interface SAPatternReference : NSObject

@property (nonatomic, readonly, strong) NSString *name;
@property (nonatomic, readonly, assign) Class klass;

- (instancetype)init NS_UNAVAILABLE;
+ (instancetype)referenceWithNamed:(NSString *)name
                             klass:(Class)klass;

@end

@implementation SAPatternReference

- (instancetype)initWithNamed:(NSString *)name
                        klass:(Class)klass;
{ 
  self = [super init];
  if (self != nil) {
    _name = [name copy];
    _klass = klass;
  }
  return self;
}

+ (instancetype)referenceWithNamed:(NSString *)name
                             klass:(Class)klass
{
  return [[SAPatternReference alloc] initWithNamed:name
                                             klass:klass];
}

@end

//
// SAClassRegistration
//

@interface SAClassRegistration : NSObject

- (instancetype)init NS_UNAVAILABLE;
- (instancetype)initWithClassNamed:(NSString *)className
                   superclassNamed:(NSString *)superclassName;

- (Class)registerClass;

- (void)registerInstancePropertyWithReference:(SAPatternReference *)patternReference
                         getterExecutionBlock:(id)getterExecutionBlock
                         setterExecutionBlock:(id)setterExecutionBlock;

- (void)registerInstanceMethodWithReference:(SAPatternReference *)patternReference
                             executionBlock:(id)executionBlock;

@end

@interface SAClassRegistration ()

@property (nonatomic, readonly, assign) Class klass;
@property (nonatomic, readonly, assign) Class superklass;

@property (nonatomic, assign, getter=isKlassRegistered) BOOL klassRegistered;

@end

@implementation SAClassRegistration

- (instancetype)initWithClassNamed:(NSString *)className
                   superclassNamed:(NSString *)superclassName
{
  self = [super init];
  if (self != nil) {
    Class superklass = NSClassFromString(superclassName);
    if (superklass == NULL) {
      [[NSException exceptionWithName:NSGenericException
                               reason:[NSString stringWithFormat:@"Class `%@` not found", className]
                             userInfo:nil] raise];
    }
        
    _superklass = superklass;
    _klass = objc_allocateClassPair(_superklass, [className UTF8String], 0);
    _klassRegistered = NO;
  }
  return self;
}

- (Class)registerClass {
    if (!self.isKlassRegistered) {
        objc_registerClassPair(self.klass);
    }
    
    return self.klass;
}

#pragma mark - Methods & Properties Registration

- (void)registerInstancePropertyWithReference:(SAPatternReference *)patternReference
                         getterExecutionBlock:(id)getterExecutionBlock
                         setterExecutionBlock:(id)setterExecutionBlock
{
  [self registrationExceptionIfNeeded];
    
  Class patternClass = patternReference.klass;
    
  unsigned attributeListCount;
  objc_property_t patternProperty = class_getProperty(patternClass, [patternReference.name UTF8String]);
  objc_property_attribute_t *attributeList = property_copyAttributeList(patternProperty, &attributeListCount);
  class_addProperty(self.klass, [patternReference.name UTF8String], attributeList, attributeListCount);
  free(attributeList);
    
  NSString *getterMethodName = patternReference.name;
  [self registerInstanceMethodWithReference:[SAPatternReference referenceWithNamed:getterMethodName klass:patternClass]
                             executionBlock:getterExecutionBlock];
    
  NSString *capitalizedName = [NSString stringWithFormat:@"%@%@", [[getterMethodName substringToIndex:1] uppercaseString], [getterMethodName substringFromIndex:1]];
  NSString *setterMethodName = [NSString stringWithFormat:@"set%@:", capitalizedName];
  [self registerInstanceMethodWithReference:[SAPatternReference referenceWithNamed:setterMethodName klass:patternClass]
                             executionBlock:setterExecutionBlock];
}

- (void)registerInstanceMethodWithReference:(SAPatternReference *)patternReference
                             executionBlock:(id)executionBlock
{
  [self registrationExceptionIfNeeded];
    
  SEL patternSelector = NSSelectorFromString(patternReference.name);
  const char *patternTypeEncoding = method_getTypeEncoding(class_getInstanceMethod(patternReference.klass, patternSelector));
  class_addMethod(self.klass, patternSelector, imp_implementationWithBlock(executionBlock), patternTypeEncoding);
}

#pragma mark - Private

- (void)registrationExceptionIfNeeded {
  if (!self.isKlassRegistered) {
    return;
  }
    
  [[NSException exceptionWithName:NSGenericException
                           reason:@"Class already registered and can not being modified."
                         userInfo:nil] raise];
}

@end