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漏洞。请注意，覆盖特定方法（例如，-addFriendsObject:如果我有朋友关系）不是一个选项，因为我需要在一个类别中执行此操作，因此它适用于任何托管对象，无论修改模型和从中重建自动生成的类。

对此的需求源于这样一个事实：显然，分钟关系是有序的，而且很多（NSMutableOrderedSets）核心数据的动态方法是地狱：

方法-add<Relationship>Object，-add<Relationship>，-remove<Relationship>Object和-remove<Relationship>都会因类似异常而崩溃'NSInvalidArgumentException', reason: '*** -[NSSet intersectsSet:]: set argument is not an NSSet'
insertObject:in<Relationship>AtIndex:行的方法将会崩溃，因为CoreData实际上没有提供它们的实现。

至于 2 ，我写了一个覆盖-methodSignatureForSelector:和-forwardInvocation的类别，而不是像mutableOrderedSetValueForKey这样的关系名称，后跟实际添加或删除。

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）。所以我需要一种拦截那些选择器的方法，所以我可以通过mutableOrderedSetValueForKey实现这个行为。

任何想法如何实现它？

Answer 1

我不知道这是最好的方法（它当然不是最漂亮的东西），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

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？

1 个答案: