ios - 将 findObjectsInBackgroundWithBlock 的结果传递到变量中

Question

我正在尝试将查询结果传递到变量数组

var petitions = [PFObject] = []

然后返回结果。我如何在 Swift 中做到这一点？

func getPetitions(employeeId: String, employeeBusiness: String) -> [PFObject] {

    var petitions: [PFObject] = []

    var query = PFQuery(className:"Petitions")
    query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
    query.whereKey("employeeId", equalTo:employeeId)
    query.whereKey("employeeBusiness", equalTo:employeeBusiness)
    query.findObjectsInBackgroundWithBlock {
        (objects: [AnyObject]?, error: NSError?) -> Void in
        if error == nil {
            if let objects = objects as? [PFObject] {
                NSLog("Successfully retrieved \(objects.count) petitions.")
                for object in objects {
                    petitions.append(object)
                }
            }
        }
    }

    return petitions
}

Answer 1

查询是异步传递的，这意味着当您返回请求时，query.findObjectsInBackgroundWithBlock可能不会(99%不会)完成。

你可以直接在函数中做你想做的事情:

var petitions: [PFObject] = [] //class variable

func getPetitions(employeeId: String, employeeBusiness: String) {

    var query = PFQuery(className:"Petitions")
    query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
    query.whereKey("employeeId", equalTo:employeeId)
    query.whereKey("employeeBusiness", equalTo:employeeBusiness)
    query.findObjectsInBackgroundWithBlock {
        (objects: [AnyObject]?, error: NSError?) -> Void in
        if error == nil {
            if let objects = objects as? [PFObject] {
                NSLog("Successfully retrieved \(objects.count) petitions.")
                for object in objects {
                    self.petitions.append(object)
                }
                // update UI
                // or just do whatever you want with the petitions.
            }
        }
    }
}

或者你可以编写一个 block 函数:

func getPetitions(employeeId: String, employeeBusiness: String, block:PFArrayResultBlock) {

        var query = PFQuery(className:"Petitions")
        query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
        query.whereKey("employeeId", equalTo:employeeId)
        query.whereKey("employeeBusiness", equalTo:employeeBusiness)
        query.findObjectsInBackgroundWithBlock(block)
        }
    }

调用它:

getPetitions("employeeId", "employeeBusiness", block: {
    (objects: [AnyObject]?, error: NSError?) -> Void in
            // do whatever you want with your objects..
            // update UI
            // or just do whatever you want with the petitions.
})

解决这个问题的另一种方法是同步查询:

func getPetitions(employeeId: String, employeeBusiness: String) -> [PFObject] {
    var query = PFQuery(className:"Petitions")
    query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
    query.whereKey("employeeId", equalTo:employeeId)
    query.whereKey("employeeBusiness", equalTo:employeeBusiness)
    var objects = query.findObjects()
    if let petititons = objects as? [PFObject] {
        return petititons
    } else {
        return [PFObject]() // return an empty pf object array. If you want, return nil.. but the return value must be [PFObject]? if you do this.
    }
}