Sheet弹窗中TransactionCreateView重复调用问题排查求助

有两个配置几乎完全相同的SwiftUI项目，其中一个在展示sheet弹窗时，TransactionCreateView(sheet: self.sheet)会被反复调用（已通过断点确认）。推测存在触发视图重复重绘的因素，但另一个同配置项目无此问题。相关代码如下：

TransactionsView #

struct TransactionsView: View {

    @Environment(\.modelContext) private var modelContext
    
    let sheet: Sheet
    
    @Query private var transactions: [Transaction]
    
    @State private var showCreate = false

    init(sheet: Sheet) {
        // init code to query for transactions matching Sheet ID
    }

    var body: some View {
        List {
            ForEach(transactions) { tx in
                // Standard row stuff
            }
            .onDelete(perform: deleteTxs)
        }
        .toolbar {
            ToolbarItem {
                Button(action: addTransaction) {
                    Label("Add", systemImage: "plus")
                }
            }
        }
        .sheet(isPresented: $showCreate) {
            TransactionCreateView(sheet: self.sheet)
            .presentationDetents([.medium, .large])
        }
    }
    
    private func addTransaction() {
        withAnimation {
            showCreate.toggle()
        }
    }
    
    private func deleteTxs(offsets: IndexSet) {
        withAnimation {
            for index in offsets {
                modelContext.delete(transactions[index])
            }
        }
    }
}

TransactionCreateView #

struct TransactionCreateView: View {
    
    @Environment(\.dismiss) var dismiss
    @Environment(\.modelContext) private var modelContext
    
    @State private var transaction: Transaction
    @State private var notesText: String = ""

    let sheet: Sheet
    
    init(sheet: Sheet) {
        self.sheet = sheet
        self.transaction = Transaction(sheet: self.sheet)
    }
    
    var body: some View {
        Form {
            Picker("Type", selection: $transaction.type) {
                ForEach(TransactionType.allCases, id: \.self) { type in
                    Text(type.rawValue.capitalized)
                        .tag(type)
                }
            }
            .pickerStyle(.segmented)
            
            TextField("Amount", value: $transaction.value, format: .number)

            TextField("Notes", text: $notesText, prompt: Text("What was this for?"))

            Button("Add") {
                withAnimation {
                    transaction.notes = notesText.isEmpty ? nil : notesText
                    modelContext.insert(transaction)
                }
                dismiss()
            }
        }
        .onAppear {
            notesText = transaction.notes ?? ""
        }
    }
}

Model文件 #

@Model
final class Transaction {
    var timestamp: Date
    var value: Double
    var type: TransactionType
    var notes: String?
    
    @Relationship(inverse: \Sheet.transactions) var sheet: Sheet?
}

enum TransactionType: String, Codable, CaseIterable {
    case income
    case expense
}

@Model
final class Sheet {
    var timestamp: Date
    var title: String
    
    var transactions: [Transaction]
}

1. Sheet对象引用不稳定
   Sheet是@Model引用类型，如果父视图传递的Sheet实例发生了不必要的引用变更（比如父视图重绘时重新创建了Sheet对象，或Sheet的属性修改导致SwiftUI判定其为新对象），会触发TransactionsView重绘，进而导致sheet闭包内的TransactionCreateView反复初始化。

2. @Query更新触发重绘连锁反应
   TransactionsView中的@Query会监听Transaction数据变化，当在TransactionCreateView中插入新Transaction时，@Query会更新transactions数组，触发TransactionsView重绘。此时如果self.sheet被SwiftUI判定为依赖变化，就会重新创建TransactionCreateView。

3. TransactionCreateView初始化逻辑问题
   在init中直接创建Transaction并赋值给@State，这种方式会导致父视图重绘时，TransactionCreateView的@State属性被重新初始化，进而触发视图反复创建。

4. 父视图不必要重绘
   若TransactionsView的父视图存在频繁变化的@State/@Binding属性，会导致整个视图树重绘，间接影响sheet内的视图初始化。

• 稳定Sheet对象引用：检查父视图传递Sheet的方式，用@State/@StateObject持有Sheet实例，避免频繁创建新引用。
• 调整Transaction初始化时机：将Transaction的创建移到onAppear中，避免在init中初始化@State属性：

  struct TransactionCreateView: View {
      // ... 其他属性
      @State private var transaction: Transaction?
  
      init(sheet: Sheet) {
          self.sheet = sheet
      }
  
      var body: some View {
          Form {
              // ... 表单内容
          }
          .onAppear {
              transaction = Transaction(sheet: sheet)
              notesText = transaction?.notes ?? ""
          }
      }
  }
  

• 添加视图标识稳定化：在TransactionCreateView上添加.id(showCreate)，确保仅当弹窗状态变化时才重新创建视图：

  .sheet(isPresented: $showCreate) {
      TransactionCreateView(sheet: self.sheet)
          .presentationDetents([.medium, .large])
          .id(showCreate)
  }
  

• 排查父视图重绘原因：检查父视图中是否存在不必要的状态变化，减少无意义的视图树重绘。

内容的提问来源于stack exchange，提问作者Dovizu