ios - 有没有办法以通用方式替换关系的添加和删除方法的核心数据实现？

Question

请注意:这与 this question 不是同一个问题，因为我已经知道这源于 Apple 错误。请注意，覆盖特定方法(例如，-addFriendsObject:，如果我有 friend 关系)不是一种选择，因为我需要在类别中执行此操作，以便它适用于任何托管对象，而不管修改模型和重建从中自动生成类。

对此的需求源于这样一个事实，即显然在使关系有序化的那一刻，对多(NSMutableOrderedSets)核心数据动态方法就会陷入困境:

1. 方法 -add<Relationship>Object , -add<Relationship> , -remove<Relationship>Object和 -remove<Relationship>都会崩溃，异常相似 'NSInvalidArgumentException', reason: '*** -[NSSet intersectsSet:]: set argument is not an NSSet'
2. 按照 insertObject:in<Relationship>AtIndex: 的方法反而会崩溃，因为 CoreData 实际上没有为它们提供任何实现。

至于2，我写了一个覆盖-methodSignatureForSelector:的类别和 -forwardInvocation而是做类似 mutableOrderedSetValueForKey 的事情对于关系名称，后跟实际的添加或删除。

现在对于 1，问题是 CoreData 实际上为这些方法提供了实现(尽管它们不是有序集的正确实现)。所以我也需要一种拦截这些选择器的方法，这样我就可以通过 mutableOrderedSetValueForKey 实现行为。

有什么想法可以实现吗？

Answer 1

我不知道这是最好的方法(它肯定不是有史以来最漂亮的方法)，但它完成了工作:

#import "NSManagedObject+OrderedSets.h"
#import <objc/runtime.h>

@implementation NSManagedObject (OrderedSets)

+ (void)swizzleMethod:(SEL)originalSelector with:(SEL)replacementSelector
{
    const char *methodTypeEncoding = method_getTypeEncoding(class_getInstanceMethod([self class], originalSelector));
    class_replaceMethod(self,
                        originalSelector,
                        class_getMethodImplementation(self, replacementSelector),
                        methodTypeEncoding);
}

+ (void)initialize
{
    NSEntityDescription *selfEntity = // get a hold of your NSManagedObjectContext and from its entities grab model.entitiesByName[NSStringFromClass(self)] ... 
    for (NSString *rKey in [selfEntity relationshipsByName]) {
        NSRelationshipDescription *r = selfEntity.relationshipsByName[rKey];
        if (r.isOrdered) {
            NSString *rKeyFirstCaps = [[rKey substringToIndex:1] capitalizedString];
            NSString *capitalizedKey = [rKey stringByReplacingCharactersInRange:NSMakeRange(0,1) withString:rKeyFirstCaps];
            NSString *addSelectorString = [NSString stringWithFormat:@"add%@Object:", capitalizedKey];
            NSString *removeSelectorString = [NSString stringWithFormat:@"remove%@Object:", capitalizedKey];
            [self swizzleMethod:NSSelectorFromString(addSelectorString) with:@selector(addOrRemoveObjectInOrderedSet:)];
            [self swizzleMethod:NSSelectorFromString(removeSelectorString) with:@selector(addOrRemoveObjectInOrderedSet:)];
        }
    }
}

- (void)addOrRemoveObjectInOrderedSet:(NSManagedObject*)object
{
    NSString *selectorString = NSStringFromSelector(_cmd);
    NSString *prefix = [selectorString hasPrefix:@"add"] ? @"add" : @"remove";
    selectorString = [selectorString stringByReplacingCharactersInRange:[selectorString rangeOfString:prefix] withString:@""];
    selectorString = [selectorString stringByReplacingCharactersInRange:[selectorString rangeOfString:@"Object" options:NSBackwardsSearch] withString:@""];
    selectorString = [selectorString substringToIndex:selectorString.length - 1];
    NSString *selectorFirstLowerCase = [[selectorString substringToIndex:1] lowercaseString];
    NSString *camelCasedKey = [selectorString stringByReplacingCharactersInRange:NSMakeRange(0,1) withString:selectorFirstLowerCase];

    if ([prefix isEqualToString:@"add"]) {
        [[self mutableOrderedSetValueForKey:camelCasedKey] addObject:object];
    }
    else {
        [[self mutableOrderedSetValueForKey:camelCasedKey] removeObject:object];
    }
}

@end