Question

如何在Swift谓词中组合混合AND OR条件。我有以下查询

 Select * from tblTemp where dept == 1 && (subdept == 11 || subdept == 12)

我可以用相同的运算符编写两个谓词，但不知道如何组合它们

    let deptPredicate = NSPredicate(format: "dept == %@", 1)
    let subdeptPredicate1 = NSPredicate(format: "subdept = %@", 11)
    let subdeptPredicate2 = NSPredicate(format: "subdept = %@", 12)
    let andPredicate = NSCompoundPredicate(type: NSCompoundPredicate.LogicalType.and, subpredicates: [deptPredicate, subdeptPredicate1])

Answer 1

NSCompoundPredicate是NSPredicate的子类，意思是结果 NSCompoundPredicate(type:subpredicates:)可用于其他化合物谓词。

但请注意，%@格式占位符需要NSObject 实例：

let deptPredicate = NSPredicate(format: "dept == %@", 1 as NSNumber)
let subdeptPredicate1 = NSPredicate(format: "subdept = %@", 11 as NSNumber)
let subdeptPredicate2 = NSPredicate(format: "subdept = %@", 12 as NSNumber)

let orPredicate = NSCompoundPredicate(type: .or,
                                      subpredicates: [subdeptPredicate1, subdeptPredicate2])

let andPredicate = NSCompoundPredicate(type: .and,
                                       subpredicates: [deptPredicate, orPredicate])

或者，对整数使用%ld格式：

let deptPredicate = NSPredicate(format: "dept == %ld", 1)
// ... etc.

还有便利初始化器：

let orPredicate = NSCompoundPredicate(orPredicateWithSubpredicates:
    [subdeptPredicate1, subdeptPredicate2])

let andPredicate = NSCompoundPredicate(andPredicateWithSubpredicates:
    [deptPredicate, orPredicate])

复合谓词对于组合动态集非常有用运行时的条件。另一方面，如果只有值发生变化那么你可以简单地在谓词中使用“AND”和“OR” 格式字符串：

NSPredicate(format: "dept == %ld AND (subdept = %ld OR subdept = %ld)", 1, 11, 12)

最后请注意，您可以使用#keyPath指令 %K占位符，以便编译器填充正确的属性名称（从而减少印刷错误的可能性）：

let deptPredicate = NSPredicate(format: "%K == %ld", #keyPath(MyEntity.dept), 1)

Swift组合谓词LogicalType AND OR

1 个答案: