【转】Objective-C Runtime 消息机制

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objc_msgSend(receiver, selector)

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objc_msgSend(receiver, selector, arg1, arg2, ...)

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id objc_msgSend ( id self, SEL op, ... );

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typedef struct objc_selector *SEL;

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typedef struct objc_object *id;

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struct objc_object { Class isa; };

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typedef struct objc_class *Class;

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struct objc_class {
Class isa  OBJC_ISA_AVAILABILITY;

#if !__OBJC2__
Class super_class                                        OBJC2_UNAVAILABLE;
const char *name                                         OBJC2_UNAVAILABLE;
long version                                             OBJC2_UNAVAILABLE;
long info                                                OBJC2_UNAVAILABLE;
long instance_size                                       OBJC2_UNAVAILABLE;
struct objc_ivar_list *ivars                             OBJC2_UNAVAILABLE;
struct objc_method_list **methodLists                    OBJC2_UNAVAILABLE;
struct objc_cache *cache                                 OBJC2_UNAVAILABLE;
struct objc_protocol_list *protocols                     OBJC2_UNAVAILABLE;
#endif

} OBJC2_UNAVAILABLE;

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struct objc_ivar_list {
int ivar_count                                           OBJC2_UNAVAILABLE;
#ifdef __LP64__
int space                                                OBJC2_UNAVAILABLE;
#endif
/* variable length structure */
struct objc_ivar ivar_list[1]                            OBJC2_UNAVAILABLE;
}                                                            OBJC2_UNAVAILABLE;

struct objc_method_list {
struct objc_method_list *obsolete                        OBJC2_UNAVAILABLE;

int method_count                                         OBJC2_UNAVAILABLE;
#ifdef __LP64__
int space                                                OBJC2_UNAVAILABLE;
#endif
/* variable length structure */
struct objc_method method_list[1]                        OBJC2_UNAVAILABLE;
}

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typedef struct objc_method *Method;

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struct objc_method {
SEL method_name                                          OBJC2_UNAVAILABLE;
char *method_types                                       OBJC2_UNAVAILABLE;
IMP method_imp                                           OBJC2_UNAVAILABLE;
}                                                            OBJC2_UNAVAILABLE;

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typedef struct objc_ivar *Ivar;

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struct objc_ivar {
char *ivar_name                                          OBJC2_UNAVAILABLE;
char *ivar_type                                          OBJC2_UNAVAILABLE;
int ivar_offset                                          OBJC2_UNAVAILABLE;
#ifdef __LP64__
int space                                                OBJC2_UNAVAILABLE;
#endif
}                                                            OBJC2_UNAVAILABLE;

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typedef id (*IMP)(id, SEL, ...);

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typedef struct objc_cache *Cache

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struct objc_cache {
unsigned int mask /* total = mask + 1 */                 OBJC2_UNAVAILABLE;
unsigned int occupied                                    OBJC2_UNAVAILABLE;
Method buckets[1]                                        OBJC2_UNAVAILABLE;
};

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typedef struct objc_property *Property;
typedef struct objc_property *objc_property_t;//这个更常用

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objc_property_t *class_copyPropertyList(Class cls, unsigned int *outCount)
objc_property_t *protocol_copyPropertyList(Protocol *proto, unsigned int *outCount)

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@interface Lender : NSObject {
float alone;
}
@property float alone;
@end

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id LenderClass = objc_getClass("Lender");
unsigned int outCount;
objc_property_t *properties = class_copyPropertyList(LenderClass, &outCount);

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const char *property_getName(objc_property_t property)

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objc_property_t class_getProperty(Class cls, const char *name)
objc_property_t protocol_getProperty(Protocol *proto, const char *name, BOOL isRequiredProperty, BOOL isInstanceProperty)

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const char *property_getAttributes(objc_property_t property)

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id LenderClass = objc_getClass("Lender");
unsigned int outCount, i;
objc_property_t *properties = class_copyPropertyList(LenderClass, &outCount);
for (i = 0; i < outCount; i++) {
objc_property_t property = properties[i];
fprintf(stdout, "%s %s\n", property_getName(property), property_getAttributes(property));
}

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- strange
{
id  target = getTheReceiver();
SEL method = getTheMethod();

if ( target == self || method == _cmd )
return nil;
return [target performSelector:method];
}

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struct objc_super { id receiver; Class class; };

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void (*setter)(id, SEL, BOOL);
int i;

setter = (void (*)(id, SEL, BOOL))[target
methodForSelector:@selector(setFilled:)];
for ( i = 0 ; i < 1000 ; i++ )
setter(targetList[i], @selector(setFilled:), YES);

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@dynamic propertyName;

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void dynamicMethodIMP(id self, SEL _cmd) {
// implementation ....
}
@implementation MyClass
+ (BOOL)resolveInstanceMethod:(SEL)aSEL
{
if (aSEL == @selector(resolveThisMethodDynamically)) {
class_addMethod([self class], aSEL, (IMP) dynamicMethodIMP, "v@:");
return YES;
}
return [super resolveInstanceMethod:aSEL];
}
@end

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- (id)forwardingTargetForSelector:(SEL)aSelector
{
if(aSelector == @selector(mysteriousMethod:)){
return alternateObject;
}
return [super forwardingTargetForSelector:aSelector];
}

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- (void)forwardInvocation:(NSInvocation *)anInvocation
{
if ([someOtherObject respondsToSelector:
[anInvocation selector]])
[anInvocation invokeWithTarget:someOtherObject];
else
[super forwardInvocation:anInvocation];
}

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if ( [aWarrior respondsToSelector:@selector(negotiate)] )
...

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- (BOOL)respondsToSelector:(SEL)aSelector
{
if ( [super respondsToSelector:aSelector] )
return YES;
else {
/* Here, test whether the aSelector message can     *
* be forwarded to another object and whether that  *
* object can respond to it. Return YES if it can.  */
}
return NO;
}

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- (NSMethodSignature*)methodSignatureForSelector:(SEL)selector
{
NSMethodSignature* signature = [super methodSignatureForSelector:selector];
if (!signature) {
signature = [surrogate methodSignatureForSelector:selector];
}
return signature;
}

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void objc_setAssociatedObject ( id object, const void *key, id value, objc_AssociationPolicy policy );
id objc_getAssociatedObject ( id object, const void *key );
void objc_removeAssociatedObjects ( id object );

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enum {
OBJC_ASSOCIATION_ASSIGN  = 0,
OBJC_ASSOCIATION_RETAIN_NONATOMIC  = 1,
OBJC_ASSOCIATION_COPY_NONATOMIC  = 3,
OBJC_ASSOCIATION_RETAIN  = 01401,
OBJC_ASSOCIATION_COPY  = 01403
};

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#import <objc/runtime.h>

@implementation UIViewController (Tracking)

+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class aClass = [self class];

SEL originalSelector = @selector(viewWillAppear:);
SEL swizzledSelector = @selector(xxx_viewWillAppear:);

Method originalMethod = class_getInstanceMethod(aClass, originalSelector);
Method swizzledMethod = class_getInstanceMethod(aClass, swizzledSelector);

// When swizzling a class method, use the following:
// Class aClass = object_getClass((id)self);
// ...
// Method originalMethod = class_getClassMethod(aClass, originalSelector);
// Method swizzledMethod = class_getClassMethod(aClass, swizzledSelector);

BOOL didAddMethod =
class_addMethod(aClass,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));

if (didAddMethod) {
class_replaceMethod(aClass,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
});
}

#pragma mark - Method Swizzling

- (void)xxx_viewWillAppear:(BOOL)animated {
[self xxx_viewWillAppear:animated];
NSLog(@"viewWillAppear: %@", self);
}

@end

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// When swizzling a class method, use the following:
// Class aClass = object_getClass((id)self);
// ...
// Method originalMethod = class_getClassMethod(aClass, originalSelector);
// Method swizzledMethod = class_getClassMethod(aClass, swizzledSelector);

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IMP imp1 = method_getImplementation(m1);
IMP imp2 = method_getImplementation(m2);
method_setImplementation(m1, imp2);
method_setImplementation(m2, imp1);

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- (void)replacementReceiveMessage:(const struct BInstantMessage *)arg1 {
NSLog(@"arg1 is %@", arg1);
[self replacementReceiveMessage:arg1];
}
+ (void)load {
SEL originalSelector = @selector(ReceiveMessage:);
SEL overrideSelector = @selector(replacementReceiveMessage:);
Method originalMethod = class_getInstanceMethod(self, originalSelector);
Method overrideMethod = class_getInstanceMethod(self, overrideSelector);
if (class_addMethod(self, originalSelector, method_getImplementation(overrideMethod), method_getTypeEncoding(overrideMethod))) {
class_replaceMethod(self, overrideSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, overrideMethod);
}
}

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extension SKNode {

class func yxy_swizzleAddChild() {
let cls = SKNode.self
let originalSelector = Selector("addChild:")
let swizzledSelector = Selector("yxy_addChild:")
let originalMethod = class_getInstanceMethod(cls, originalSelector)
let swizzledMethod = class_getInstanceMethod(cls, swizzledSelector)
method_exchangeImplementations(originalMethod, swizzledMethod)
}

class func yxy_swizzleRemoveFromParent() {
let cls = SKNode.self
let originalSelector = Selector("removeFromParent")
let swizzledSelector = Selector("yxy_removeFromParent")
let originalMethod = class_getInstanceMethod(cls, originalSelector)
let swizzledMethod = class_getInstanceMethod(cls, swizzledSelector)
method_exchangeImplementations(originalMethod, swizzledMethod)
}

func yxy_addChild(node: SKNode) {
if node.parent == nil {
self.yxy_addChild(node)
}
else {
println("This node has already a parent!\(node.name)")
}
}

func yxy_removeFromParent() {
if parent != nil {
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.yxy_removeFromParent()
})
}
else {
println("This node has no parent!\(name)")
}
}

}

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SKNode.yxy_swizzleAddChild()
SKNode.yxy_swizzleRemoveFromParent()