领域可可:通过PK查找多个对象

长期潜伏者，第一次提问者。

我正在一个项目中使用 Realm Cocoa（来自 Realm.io），并且正在努力通过 PK 执行搜索。假设我有一个名为 RLMFoo 的实体，它有一个叫做 bar 的主键。我还有一个PK列表，假设存储在一个数组中：

NSArray *primaryKeys = @[@"bar1", @"bar2", @"bar3"]

有没有办法在单个查询中从我的领域检索类 RLMFoo 的所有实体？

到目前为止，我已经尝试过：

格式为：[RLMFoo objectsInRealm:realm withPredicate:[NSPredicate predicateWithFormat:@"bar IN %@", primaryKeys]];的谓词
境界：[RLMFoo objectsInRealm:realm where:@"bar IN %@", strippedIds];
带块的谓词：

NSPredicate *predicate = [NSPredicate predicateWithBlock:^BOOL(id
evaluatedObject, NSDictionary *bindings) {
                    RLMFoo *foo = (RLMFoo *)evaluatedObject;
                    return [primaryKeys containsObject:foo.bar];
                }];
        [RLMFoo objectsInRealm:realm withPredicate:predicate];

但到目前为止，我发现唯一有效的方法是查询每个主键值的领域并聚合结果，这似乎很慢：

NSMutableArray *results = [NSMutableArray new];
for (NSString *primaryKey in primaryKeys) {
    RLMFoo *obj = [RLMFoo objectInRealm:realm forPrimaryKey:primaryKey];
    if (obj) {
        [results addObject:obj];
    }
}

有谁知道更好的方法吗？

======

=== 解释为什么前三种方法不起作用 =======

1）从异常消息中似乎可以明显看出这不起作用的原因：IN仅取2个值，尽管IN的SQL版本应根据需要取尽可能多的值。从 RLMQueryUtil.mm 的源代码中可以看出，这同样适用于 BETWEEN 运算符：

        if (compp.predicateOperatorType == NSBetweenPredicateOperatorType || compp.predicateOperatorType == NSInPredicateOperatorType) {
        // Inserting an array via %@ gives NSConstantValueExpressionType, but
        // including it directly gives NSAggregateExpressionType
        if (exp1Type != NSKeyPathExpressionType || (exp2Type != NSAggregateExpressionType && exp2Type != NSConstantValueExpressionType)) {
            @throw RLMPredicateException(@"Invalid predicate",
                                         @"Predicate with %s operator must compare a KeyPath with an aggregate with two values",
                                         compp.predicateOperatorType == NSBetweenPredicateOperatorType ? "BETWEEN" : "IN");
        }

下面是堆栈跟踪：

*** Terminating app due to uncaught exception 'Invalid predicate', reason: 'Predicate with IN operator must compare a KeyPath with an aggregate with two values'
*** First throw call stack:
(
    0   CoreFoundation      0x03334946 __exceptionPreprocess + 182
    1   libobjc.A.dylib     0x0292aa97 objc_exception_throw + 44
    2   <redacted>          0x00190569 _ZN12_GLOBAL__N_127update_query_with_predicateEP11NSPredicateP9RLMSchemaP15RLMObjectSchemaRN7tightdb5QueryE + 2553
    3   <redacted>          0x0018f7ea _Z27RLMUpdateQueryWithPredicatePN7tightdb5QueryEP11NSPredicateP9RLMSchemaP15RLMObjectSchema + 378
    4   <redacted>          0x0018b23c _Z13RLMGetObjectsP8RLMRealmP8NSStringP11NSPredicate + 748
    5   <redacted>          0x0017d721 +[RLMObject objectsInRealm:withPredicate:] + 161

2）这在原因和堆栈跟踪上非常相似：

*** Terminating app due to uncaught exception 'Invalid predicate', reason: 'Predicate with IN operator must compare a KeyPath with an aggregate with two values'
*** First throw call stack:
(
    0   CoreFoundation      0x03328946 __exceptionPreprocess + 182
    1   libobjc.A.dylib     0x0291ea97 objc_exception_throw + 44
    2   <redacted>          0x00184599 _ZN12_GLOBAL__N_127update_query_with_predicateEP11NSPredicateP9RLMSchemaP15RLMObjectSchemaRN7tightdb5QueryE + 2553
    3   <redacted>          0x0018381a _Z27RLMUpdateQueryWithPredicatePN7tightdb5QueryEP11NSPredicateP9RLMSchemaP15RLMObjectSchema + 378
    4   <redacted>          0x0017f26c _Z13RLMGetObjectsP8RLMRealmP8NSStringP11NSPredicate + 748
    5   <redacted>          0x00171751 +[RLMObject objectsInRealm:withPredicate:] + 161
    6   <redacted>          0x00171465 +[RLMObject objectsInRealm:where:args:] + 213
    7   <redacted>          0x001712f3 +[RLMObject objectsInRealm:where:] + 419

3）这个又非常相似。归根结底，这是缺乏来自 Realm 对 NSPrectic 完整功能集的支持。

*** Terminating app due to uncaught exception 'Invalid predicate', reason: 'Only support compound and comparison predicates'
*** First throw call stack:
(
    0   CoreFoundation      0x03308946 __exceptionPreprocess + 182
    1   libobjc.A.dylib     0x028fea97 objc_exception_throw + 44
    2   <redacted>          0x001638bd _ZN12_GLOBAL__N_127update_query_with_predicateEP11NSPredicateP9RLMSchemaP15RLMObjectSchemaRN7tightdb5QueryE + 4397
    3   <redacted>          0x0016240a _Z27RLMUpdateQueryWithPredicatePN7tightdb5QueryEP11NSPredicateP9RLMSchemaP15RLMObjectSchema + 378
    4   <redacted>          0x0015de5c _Z13RLMGetObjectsP8RLMRealmP8NSStringP11NSPredicate + 748
    5   <redacted>          0x00150341 +[RLMObject objectsInRealm:withPredicate:] + 161

您的前两个选项应该没有问题。编写此查询的最简单方法是：

NSArray *primaryKeys = @[@"bar1", @"bar2", @"bar3"]
RLMResults *results = [RLMFoo objectsWhere:@"id IN %@", primaryKeys];

一个名为objectsWithPredicate的方法也可以工作。在使用前几种方法时，您能否分享更多代码/堆栈跟踪？我认为其他地方也发生了问题

在您的帮助下，我能够找到这种行为的原因。我的真实代码更接近：

  NSArray *primaryKeys = @[ @"bar1", @"bar2", @"bar3" ];
  NSString *primaryKeyName = @"bar";
  RLMResults *results =
      [RLMFoo objectsInRealm:self.realm
               withPredicate:[NSPredicate predicateWithFormat:@"%@ IN %@",
                                                              primaryKeyName,
                                                              primaryKeys]];

这是在方法中，PK 和 PK 名称是方法调用的参数。从理论上讲，这将允许我的类检索具有任何PK名称的任何对象。事实证明，我的错误在于假设谓词格式在这种情况下以类似于 stringWithFormat 的方式工作，并正确替换 PK 名称作为第一个参数并将 PK 数组作为第二个参数。然而，解决方案是首先组装格式字符串，然后组装谓词：

  RLMResults *results = [RLMFoo
      objectsInRealm:self.realm
       withPredicate:[NSPredicate
                         predicateWithFormat:
                             [NSString stringWithFormat:@"%@ IN %%@", primaryKeyName],
                             primaryKeys]];

谢谢Yoshyosh的时间。

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