具有多个条件和一个参数的谓词

Posted 2023-03-04

【中文标题】具有多个条件和一个参数的谓词

【英文标题】：Predicate with many conditions and one argument

【发布时间】：2018-01-03 17:53:33

【问题描述】：

我正在尝试查询联系人领域数据库，但我有一个查询字符串，我需要在谓词中重复它还是有更好的方法？

let contactResults = realm.objects(ContactRealm.self).filter("is_Contact == true AND full_name CONTAINS[c] %@ OR phone_number_one CONTAINS[c] %@ OR phone_number_two CONTAINS[c] %@ OR phone_number_three CONTAINS[c] %@ OR email_address_one CONTAINS[c] %@ OR email_address_two CONTAINS[c] %@", query, query, query, query, query, query).sorted(byKeyPath: "full_name", ascending: true)

这样的查询也被认为是一种不好的做法吗？

更新：正如这里的评论所建议的那样：

let predicateContact = NSPredicate(format: "is_Contact == true")

let fullname = NSPredicate(format: "full_name CONTAINS[c] %@", query)

let phoneNumber = NSPredicate(format: "phone_number_one CONTAINS[c] %@", query)

let phonenumbertwo = NSPredicate(format: "phone_number_one CONTAINS[c] %@", query)

let email = NSPredicate(format: "phone_number_one CONTAINS[c] %@", query)

let secondEmail = NSPredicate(format: "phone_number_one CONTAINS[c] %@", query)

let compoundOr = NSCompoundPredicate(orPredicateWithSubpredicates: [fullname, phoneNumber, phonenumbertwo, email, secondEmail])

let compound = NSCompoundPredicate(type: .and, subpredicates: [predicateContact, compoundOr])

let contactResults = realm.objects(ContactRealm.self).filter(compound).sorted(byKeyPath: "full_name", ascending: true)

【问题讨论】：

当过滤这样的数据时，很容易迷失在谓词上，因此调试非常困难。我绝对建议您使用NSCompoundPredicate 来组合每个单独的谓词。还要避免像is_Contact == true 这样的任何查询，而不是NSPredicate(format: "is_Contact == %@", true)。

【参考方案1】：

由于您的谓词看起来相同并且仅显示属性名称的差异，因此我建议创建一个属性名称数组。然后，您可以通过遍历名称为每个名称创建一个NSPredicate。

let attributes = ["full_name", "phone_number_one", "phone_number_two", "phone_number_three", "email_address_one", "email_address_two"]
let contactPredicateArray = parameters.map 
    NSPredicate("\($0) CONTAINS[c] %@", query)

let contactPredicate = NSCompoundPredicate(orPredicateWithSubpredicates: contactPredicateArray)
let isContactPredicte = NSPredicate(format: "is_Contact == %@", true)
let predicate = NSCompoundPredicate(type: .and, subpredicates: [isContactPredicte, contactPredicate])

这样，代码更加灵活，因为可以通过修改 attributes 数组轻松地为谓词删除或添加单个属性。它也更具可读性，因为所有属性都在一行中定义，而不是到处定义。