英文:
Query() in view with model container attached shows error saying it does not have a model container
问题
我在视图上有一个函数，它的环境中有一个 modelContext，并且可以成功地向模型容器添加数据。但是当我在同一个函数中尝试运行 Query() 函数调用时，我在控制台上收到以下消息：
在视图的环境中设置 .modelContext 以使用 Query
对于我可能做错了什么，有什么想法吗？
代码基本如下：
let currentTrainPredicate = #Predicate<Train> { train in
train.number == currentTrainNumber
}
// 如果存在该值，则更新它
if let currentTrain = Query(filter: currentTrainPredicate).wrappedValue.first {
currentTrain.dateViewed = Date()
} else {
self.train.dateViewed = Date()
modelContext.insert(self.train)
}
英文:
I have a function on a view that has a modelContext on its environment and that can successfully add data to the model container. But when in that same function I try to run a Query() function call I get this message on the console:
Set a .modelContext in view's environment to use Query
Any idea on what I might be doing wrong?
The code is basically this:
let currentTrainPredicate = #Predicate<Train> { train in
train.number == currentTrainNumber
}
// Update the value if it exists
if let currentTrain = Query(filter: currentTrainPredicate).wrappedValue.first {
currentTrain.dateViewed = Date()
} else {
self.train.dateViewed = Date()
modelContext.insert(self.train)
}
答案1
得分: 1
让我来帮你翻译这段代码：
如果你在一个函数中进行这个操作，那么请使用 [FetchDescriptor](https://developer.apple.com/documentation/swiftdata/fetchdescriptor) 而不是一个 Query，因为 @Query 是一个属性包装器，所以你只在声明属性时使用它。
let descriptor = FetchDescriptor<Train>(predicate: currentTrainPredicate)
let currentTrain = try modelContext.fetch(descriptor).first
英文:
If you are doing this in a function then use a FetchDescriptor instead of a Query since @Query is a property wrapper so you only use it when declaring a property.
let descriptor = FetchDescriptor<Train>(predicate: currentTrainPredicate)
let currentTrain = try modelContext.fetch(descriptor).first
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