获取包含特定 Key 的 NSArray 中的所有 NSArray

Question

我有一个输出以下内容的 NSArray：

(
    {
    category = 1;
    categoryname = Random;
    excuse = "Enter your excuse here";
    id = 1;
    name = Jo;
},
    {
    category = 2;
    categoryname = School;
    excuse = "Enter your excuse here";
    id = 2;
    name = Jo;
},
    {
    category = 2;
    categoryname = School;
    excuse = "Enter your excuse here";
    id = 3;
    name = if;
}
)

现在您可以看到，category 有不同的值。我正在传递一个Int，我想将它与category 值进行比较，以便仅检索另一个NSArray 中某个类别中的那些对象。

这是我的代码：

func getAllExcusesData(categoryID: Int) -> NSMutableArray {
    var arr: NSMutableArray = NSMutableArray()
    for excuse in allExcusesData {
        println(excuse["category"]) // this line outputs "Optioanl(x)" - x is either 1 or 2, depending on what index I pass through
// it crashes here, at the 'if' line
        if excuse["category"] as Int == categoryID {
            var e: NSArray = excuse as NSArray
            arr.addObject(excuse)
        }
    }
    return arr
}

它在if 行崩溃，但它确实给出了错误： Thread 1:EXC_BREAKPOINT(code=EXC_1386_BPT, subcode=0x0)

如何将对象中的 category 字段与给定索引进行比较，然后将其添加到将从方法返回的新数组中？

Answer 1

下标返回AnyObject? 的可选值 - 您必须在强制转换之前将其解包或通过以下方式之一与另一个值进行比较：

if let excuseCategory: AnyObject = excuse["category"]? {
    if excuseCategory as Int == categoryID {
        // do sth
    }
}

// or if you're absolutely sure that "category" key always exists:

if excuse["category"]! as Int == categoryID {
    // do sth
}

---

考虑到Array 是NSArray 和NSMutableArray 之间的桥梁，您可以“快速化”您的代码：

func getAllExcusesData(categoryID: Int) -> NSArray {
    return (allExcusesData as [AnyObject]).filter({ excuse in
        return excuse["category"]! as Int == categoryID
    })
}