快速组合谓词LogicalType AND OR

Question

我怎样才能在Swift谓词中组合一个混合与或条件。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是的子类NSPredicate，这意味着的结果 NSCompoundPredicate(type:subpredicates:)可以在另一个复合谓词中使用。

但是请注意，%@格式占位符需要一个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，%ld对整数使用格式：

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

还有便捷的初始化程序：

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

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

复合谓词对于在运行时组合一组动态条件非常有用。另一方面，如果只有值更改，则可以在谓词格式字符串中简单地使用“ AND”和“ OR”：

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

最后请注意，可以将#keyPath指令与 %K占位符一起使用，以便编译器填写正确的属性名称（从而减少印刷错误的可能性）：

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