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/*
* Copyright 2012 Facebook
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#import "FBGraphObject.h"
#import <objc/runtime.h>
// Module Summary:
// this is the module that does the heavy lifting to implement the public-facing
// developer-model described in FBGraphObject.h, namely typed protocol
// accessors over "duck-typed" dictionaries, for interating with Facebook Graph and
// Open Graph objects and actions
//
// Message forwarding is used as described here:
// https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtForwarding.html
// in order to infer implementations for property getter
// and setter selectors, backed by objectForKey: and setObject:forKey: respectively
//
// The basic flow is straightforward, though there are a number of details;
// The flow is:
// * System doesn't recognize a selector
// * It calls methodSignatureForSelector:
// * We return a new signature if we intend to handle the selector
// * The system populates the invoke object with the old selector and the new signature
// * The system passes the invocation to forwardInvocation:
// * We swap out selectors and invoke
//
// Additional details include, deferred wrapping of objects as they are fetched by callers,
// implementations for common methods such as respondsToSelector and conformsToProtocol, as
// suggested in the previously referenced documentation
static NSString *const FBIsGraphObjectKey = @"com.facebook.FBIsGraphObjectKey";
// used internally by the category impl
typedef enum _SelectorInferredImplType {
SelectorInferredImplTypeNone = 0,
SelectorInferredImplTypeGet = 1,
SelectorInferredImplTypeSet = 2
} SelectorInferredImplType;
// internal-only wrapper
@interface FBGraphObjectArray : NSMutableArray
- (id)initWrappingArray:(NSArray *)otherArray;
- (id)graphObjectifyAtIndex:(NSUInteger)index;
- (void)graphObjectifyAll;
@end
@interface FBGraphObject ()
- (id)initWrappingDictionary:(NSDictionary *)otherDictionary;
- (void)graphObjectifyAll;
- (id)graphObjectifyAtKey:(id)key;
+ (id)graphObjectWrappingObject:(id)originalObject;
+ (SelectorInferredImplType)inferredImplTypeForSelector:(SEL)sel;
+ (BOOL)isProtocolImplementationInferable:(Protocol *)protocol checkFBGraphObjectAdoption:(BOOL)checkAdoption;
@end
@implementation FBGraphObject {
NSMutableDictionary *_jsonObject;
}
#pragma mark Lifecycle
- (id)initWrappingDictionary:(NSDictionary *)jsonObject {
self = [super init];
if (self) {
if ([jsonObject isKindOfClass:[FBGraphObject class]]) {
// in this case, we prefer to return the original object,
// rather than allocate a wrapper
// we are about to return this, better make it the caller's
[jsonObject retain];
// we don't need self after all
[self release];
// no wrapper needed, returning the object that was provided
return (FBGraphObject*)jsonObject;
} else {
_jsonObject = [[NSMutableDictionary dictionaryWithDictionary:jsonObject] retain];
}
}
return self;
}
- (void)dealloc {
[_jsonObject release];
[super dealloc];
}
#pragma mark -
#pragma mark Public Members
+ (NSMutableDictionary<FBGraphObject>*)graphObject {
return [FBGraphObject graphObjectWrappingDictionary:[NSMutableDictionary dictionary]];
}
+ (NSMutableDictionary<FBGraphObject>*)graphObjectWrappingDictionary:(NSDictionary*)jsonDictionary {
return [FBGraphObject graphObjectWrappingObject:jsonDictionary];
}
+ (BOOL)isGraphObjectID:(id<FBGraphObject>)anObject sameAs:(id<FBGraphObject>)anotherObject {
if (anObject != nil &&
anObject == anotherObject) {
return YES;
}
id anID = [anObject objectForKey:@"id"];
id anotherID = [anotherObject objectForKey:@"id"];
if ([anID isKindOfClass:[NSString class]] &&
[anotherID isKindOfClass:[NSString class]]) {
return [(NSString*)anID isEqualToString:anotherID];
}
return NO;
}
#pragma mark -
#pragma mark NSObject overrides
// make the respondsToSelector method do the right thing for the selectors we handle
- (BOOL)respondsToSelector:(SEL)sel
{
return [super respondsToSelector:sel] ||
([FBGraphObject inferredImplTypeForSelector:sel] != SelectorInferredImplTypeNone);
}
- (BOOL)conformsToProtocol:(Protocol *)protocol {
return [super conformsToProtocol:protocol] ||
([FBGraphObject isProtocolImplementationInferable:protocol
checkFBGraphObjectAdoption:YES]);
}
// returns the signature for the method that we will actually invoke
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
SEL alternateSelector = sel;
// if we should forward, to where?
switch ([FBGraphObject inferredImplTypeForSelector:sel]) {
case SelectorInferredImplTypeGet:
alternateSelector = @selector(objectForKey:);
break;
case SelectorInferredImplTypeSet:
alternateSelector = @selector(setObject:forKey:);
break;
case SelectorInferredImplTypeNone:
default:
break;
}
return [super methodSignatureForSelector:alternateSelector];
}
// forwards otherwise missing selectors that match the FBGraphObject convention
- (void)forwardInvocation:(NSInvocation *)invocation {
// if we should forward, to where?
switch ([FBGraphObject inferredImplTypeForSelector:[invocation selector]]) {
case SelectorInferredImplTypeGet: {
// property getter impl uses the selector name as an argument...
NSString *propertyName = NSStringFromSelector([invocation selector]);
[invocation setArgument:&propertyName atIndex:2];
//... to the replacement method objectForKey:
invocation.selector = @selector(objectForKey:);
[invocation invokeWithTarget:self];
break;
}
case SelectorInferredImplTypeSet: {
// property setter impl uses the selector name as an argument...
NSMutableString *propertyName = [NSMutableString stringWithString:NSStringFromSelector([invocation selector])];
// remove 'set' and trailing ':', and lowercase the new first character
[propertyName deleteCharactersInRange:NSMakeRange(0, 3)]; // "set"
[propertyName deleteCharactersInRange:NSMakeRange(propertyName.length - 1, 1)]; // ":"
NSString *firstChar = [[propertyName substringWithRange:NSMakeRange(0,1)] lowercaseString];
[propertyName replaceCharactersInRange:NSMakeRange(0, 1) withString:firstChar];
// the object argument is already in the right place (2), but we need to set the key argument
[invocation setArgument:&propertyName atIndex:3];
// and replace the missing method with setObject:forKey:
invocation.selector = @selector(setObject:forKey:);
[invocation invokeWithTarget:self];
break;
}
case SelectorInferredImplTypeNone:
default:
[super forwardInvocation:invocation];
return;
}
}
- (id)graphObjectifyAtKey:(id)key {
id object = [_jsonObject objectForKey:key];
// make certain it is FBObjectGraph-ified
id possibleReplacement = [FBGraphObject graphObjectWrappingObject:object];
if (object != possibleReplacement) {
// and if not-yet, replace the original with the wrapped object
[_jsonObject setObject:possibleReplacement forKey:key];
object = possibleReplacement;
}
return object;
}
- (void)graphObjectifyAll {
NSArray *keys = [_jsonObject allKeys];
for (NSString *key in keys) {
[self graphObjectifyAtKey:key];
}
}
#pragma mark -
#pragma mark NSDictionary and NSMutableDictionary overrides
- (NSUInteger)count {
return _jsonObject.count;
}
- (id)objectForKey:(id)key {
return [self graphObjectifyAtKey:key];
}
- (NSEnumerator *)keyEnumerator {
[self graphObjectifyAll];
return _jsonObject.keyEnumerator;
}
- (void)setObject:(id)object forKey:(id)key {
return [_jsonObject setObject:object forKey:key];
}
- (void)removeObjectForKey:(id)key {
return [_jsonObject removeObjectForKey:key];
}
#pragma mark -
#pragma mark Public Members
#pragma mark -
#pragma mark Private Class Members
+ (id)graphObjectWrappingObject:(id)originalObject {
// non-array and non-dictionary case, returns original object
id result = originalObject;
// array and dictionary wrap
if ([originalObject isKindOfClass:[NSDictionary class]]) {
result = [[[FBGraphObject alloc] initWrappingDictionary:originalObject] autorelease];
} else if ([originalObject isKindOfClass:[NSArray class]]) {
result = [[[FBGraphObjectArray alloc] initWrappingArray:originalObject] autorelease];
}
// return our object
return result;
}
// helper method used by the catgory implementation to determine whether a selector should be handled
+ (SelectorInferredImplType)inferredImplTypeForSelector:(SEL)sel {
// the overhead in this impl is high relative to the cost of a normal property
// accessor; if needed we will optimize by caching results of the following
// processing, indexed by selector
NSString *selectorName = NSStringFromSelector(sel);
int parameterCount = [[selectorName componentsSeparatedByString:@":"] count]-1;
// we will process a selector as a getter if paramCount == 0
if (parameterCount == 0) {
return SelectorInferredImplTypeGet;
// otherwise we consider a setter if...
} else if (parameterCount == 1 && // ... we have the correct arity
[selectorName hasPrefix:@"set"] && // ... we have the proper prefix
selectorName.length > 4) { // ... there are characters other than "set" & ":"
return SelectorInferredImplTypeSet;
}
return SelectorInferredImplTypeNone;
}
+ (BOOL)isProtocolImplementationInferable:(Protocol*)protocol checkFBGraphObjectAdoption:(BOOL)checkAdoption {
// first handle base protocol questions
if (checkAdoption && !protocol_conformsToProtocol(protocol, @protocol(FBGraphObject))) {
return NO;
}
if ([protocol isEqual:@protocol(FBGraphObject)]) {
return YES; // by definition
}
unsigned int count = 0;
struct objc_method_description *methods = nil;
// then confirm that all methods are required
methods = protocol_copyMethodDescriptionList(protocol,
NO, // optional
YES, // instance
&count);
if (methods) {
free(methods);
return NO;
}
@try {
// fetch methods of the protocol and confirm that each can be implemented automatically
methods = protocol_copyMethodDescriptionList(protocol,
YES, // required
YES, // instance
&count);
for (int index = 0; index < count; index++) {
if ([FBGraphObject inferredImplTypeForSelector:methods[index].name] == SelectorInferredImplTypeNone) {
// we have a bad actor, short circuit
return NO;
}
}
} @finally {
if (methods) {
free(methods);
}
}
// fetch adopted protocols
Protocol **adopted = nil;
@try {
adopted = protocol_copyProtocolList(protocol, &count);
for (int index = 0; index < count; index++) {
// here we go again...
if (![FBGraphObject isProtocolImplementationInferable:adopted[index]
checkFBGraphObjectAdoption:NO]) {
return NO;
}
}
} @finally {
if (adopted) {
free(adopted);
}
}
// protocol ran the gauntlet
return YES;
}
#pragma mark -
@end
#pragma mark internal classes
@implementation FBGraphObjectArray {
NSMutableArray *_jsonArray;
}
- (id)initWrappingArray:(NSArray *)jsonArray {
self = [super init];
if (self) {
if ([jsonArray isKindOfClass:[FBGraphObjectArray class]]) {
// in this case, we prefer to return the original object,
// rather than allocate a wrapper
// we are about to return this, better make it the caller's
[jsonArray retain];
// we don't need self after all
[self release];
// no wrapper needed, returning the object that was provided
return (FBGraphObjectArray*)jsonArray;
} else {
_jsonArray = [[NSMutableArray arrayWithArray:jsonArray] retain];
}
}
return self;
}
- (void)dealloc {
[_jsonArray release];
[super dealloc];
}
- (NSUInteger)count {
return _jsonArray.count;
}
- (id)graphObjectifyAtIndex:(NSUInteger)index {
id object = [_jsonArray objectAtIndex:index];
// make certain it is FBObjectGraph-ified
id possibleReplacement = [FBGraphObject graphObjectWrappingObject:object];
if (object != possibleReplacement) {
// and if not-yet, replace the original with the wrapped object
[_jsonArray replaceObjectAtIndex:index withObject:possibleReplacement];
object = possibleReplacement;
}
return object;
}
- (void)graphObjectifyAll {
int count = [_jsonArray count];
for (int i = 0; i < count; ++i) {
[self graphObjectifyAtIndex:i];
}
}
- (id)objectAtIndex:(NSUInteger)index {
return [self graphObjectifyAtIndex:index];
}
- (NSEnumerator *)objectEnumerator {
[self graphObjectifyAll];
return _jsonArray.objectEnumerator;
}
- (NSEnumerator *)reverseObjectEnumerator {
[self graphObjectifyAll];
return _jsonArray.reverseObjectEnumerator;
}
- (void)insertObject:(id)object atIndex:(NSUInteger)index {
[_jsonArray insertObject:object atIndex:index];
}
- (void)removeObjectAtIndex:(NSUInteger)index {
[_jsonArray removeObjectAtIndex:index];
}
- (void)addObject:(id)object {
[_jsonArray addObject:object];
}
- (void)removeLastObject {
[_jsonArray removeLastObject];
}
- (void)replaceObjectAtIndex:(NSUInteger)index withObject:(id)object {
[_jsonArray replaceObjectAtIndex:index withObject:object];
}
@end
#pragma mark -
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