我正在使用服务器端swift框架Vapor编写API。我的模型很简单。我有一个Workout表，该表与Circuit表有很多关系，该表与Exercise表有很多关系。当api使用者创建锻炼时，json包含锻炼中的所有电路和锻炼。这是一个例子：
{
...
circuits: [{
...,
exercises: [{
"title": ...
}, {
"title": ...
}]
}, {
...,
exercises: [{
"title": ...
}, {
"title": ...
}]
}]
}
我遇到的问题是，当用户在多个回路中进行相同的练习时，正在创建重复的练习。我在创建新练习之前查询数据库，但似乎所有保存操作都是异步进行的，这使我无法在保存新练习之前在数据库中检测到具有相同ID /标题的现有练习。这是我的代码：
private func saveExercise(on conn: DatabaseConnectable, with content: WorkoutCreateExerciseContent, for authUser: User) throws -> Future<Exercise> {
if let exerciseId: UUID = content.id {
return Exercise.find(exerciseId, on: conn)
.unwrap(or: Abort(.badRequest, reason: "No exercise for id: \(exerciseId.uuidString)"))
} else if let title: String = content.title, let isPublicallyVisible: Bool = content.isPublicallyVisible {
return Exercise.query(on: conn).filter(\.title == title).filter(\.directions == content.directions).first().flatMap({ (possibleMatchingExercise: Exercise?) -> Future<Exercise> in
if let matchingExercise: Exercise = possibleMatchingExercise {
return conn.future(matchingExercise)
} else {
print("xxx Found no match for \(title)")
let newExercise: Exercise = Exercise(
title: title,
directions: content.directions,
isPublicallyVisible: isPublicallyVisible
)
newExercise.userId = authUser.id
return newExercise.save(on: conn)
}
})
} else {
throw Abort(.badRequest, reason: """
Bad data for exercise. Expecting either of the following:
{
/"id/": /"some id/"
}
or
{
/"title/": /"some title/"
/"directions/": /"(optional)/",
/"isPublicallyVisible/": false
}
id takes priority over other properties.
""")
}
}
private func saveCircuit(on conn: DatabaseConnectable, with content: CircuitCreateContent, order: Int, workoutId: UUID, authUser: User) throws -> Future<Circuit> {
return try content.exercises.map({ (exerciseContent: WorkoutCreateExerciseContent) throws -> Future<Exercise> in
let createdExercise: Future<Exercise> = try self.saveExercise(
on: conn,
with: exerciseContent,
for: authUser
)
return createdExercise
})
.flatten(on: conn)
.flatMap({ (exercises: [Exercise]) -> Future<Circuit> in
let circuit: Circuit = Circuit(
workoutId: workoutId,
order: order,
exerciseDuration: content.exerciseDuration,
restDuration: content.restDuration,
exerciseIDs: exercises.compactMap({ $0.id })
)
return circuit.save(on: conn)
})
}
func saveWorkout(_ conn: DatabaseConnectable, _ authentiatedUser: User, _ content: WorkoutCreateContent) throws -> Future<Workout> {
let workout: Workout = content.makeWorkout()
workout.userId = authentiatedUser.id
// First save the exercises
let createdWorkout: Future<Workout> = workout.save(on: conn).flatMap({ (savedWorkout: Workout) -> Future<Workout> in
let createdCircuits: Future<[Circuit]> = try content.circuits.enumerated().map({ (order: Int, circuitContent: CircuitCreateContent) throws -> Future<Circuit> in
let createdCircuit: Future<Circuit> = try self.saveCircuit(
on: conn, with: circuitContent,
order: order,
workoutId: savedWorkout.id!,
authUser: authentiatedUser
)
return createdCircuit
})
.flatten(on: conn)
return createdCircuits.then({ _ -> Future<Workout> in
return conn.future(savedWorkout)
})
})
return createdWorkout
}
有人看到我在这里想念的东西吗？有没有办法在开始新的Future之前等待Future完成？我是Vapor的新手，所以我对Vapor的流利api不太熟悉。
假设我们有两种假想的方法返回Future<>
func randomUInt() -> Future<UInt> { ... }
func multiply(value: UInt, by multiplier: UInt) -> Future<UInt> { ... }
并且我们想将随机数乘以5，但是如果随机数为零或1则要抛出错误。因此，在调用multiply(value: ,by: )方法之前，我们需要等待随机数。
let result: Future<UInt> = randomUInt().flatMap { (value) -> Future<UInt> in
guard value > 1 else { throw YourError }
return multiply(value: value, by: 5)
}