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有一個Basket，它存儲List<Fruit>。每個Fruit有一個Pip。如果我保存這個關係，以後檢索時，ForeignKeyPipId具有價值，但對象Pip是null，儘管我用CascadeRead。SQLite：從列表中的對象中檢索子元素
如果我嘗試使用上FruitListCascadeOperation.All我得到Constraint
at SQLite.PreparedSqlLiteInsertCommand.ExecuteNonQuery (System.Object[] source) [0x00116] in /Users/fak/Dropbox/Projects/sqlite-net/src/SQLite.cs:2507
at SQLite.SQLiteConnection.Insert (System.Object obj, System.String extra, System.Type objType) [0x0014b] in /Users/fak/Dropbox/Projects/sqlite-net/src/SQLite.cs:1386
at SQLite.SQLiteConnection.Insert (System.Object obj) [0x00008] in /Users/fak/Dropbox/Projects/sqlite-net/src/SQLite.cs:1224
at SQLiteNetExtensions.Extensions.WriteOperations.InsertElement (SQLite.SQLiteConnection conn, System.Object element, System.Boolean replace, System.Reflection.PropertyInfo primaryKeyProperty, System.Boolean isAutoIncrementPrimaryKey, System.Collections.Generic.ISet`1[T] objectCache) [0x0005a] in C:\home\mk\work\frameworks\sqlite-net-extensions\SQLiteNetExtensions\Extensions\WriteOperations.cs:270
at SQLiteNetExtensions.Extensions.WriteOperations.InsertElements (SQLite.SQLiteConnection conn, System.Collections.IEnumerable elements, System.Boolean replace, System.Collections.Generic.ISet`1[T] objectCache) [0x00069] in C:\home\mk\work\frameworks\sqlite-net-extensions\SQLiteNetExtensions\Extensions\WriteOperations.cs:238
at SQLiteNetExtensions.Extensions.WriteOperations.InsertValue (SQLite.SQLiteConnection conn, System.Object value, System.Boolean replace, System.Boolean recursive, System.Collections.Generic.ISet`1[T] objectCache) [0x0002c] in C:\home\mk\work\frameworks\sqlite-net-extensions\SQLiteNetExtensions\Extensions\WriteOperations.cs:219
at SQLiteNetExtensions.Extensions.WriteOperations.InsertChildrenRecursive (SQLite.SQLiteConnection conn, System.Object element, System.Boolean replace, System.Boolean recursive, System.Collections.Generic.ISet`1[T] objectCache) [0x0004c] in C:\home\mk\work\frameworks\sqlite-net-extensions\SQLiteNetExtensions\Extensions\WriteOperations.cs:200
at SQLiteNetExtensions.Extensions.WriteOperations.InsertWithChildrenRecursive (SQLite.SQLiteConnection conn, System.Object element, System.Boolean replace, System.Boolean recursive, System.Collections.Generic.ISet`1[T] objectCache) [0x0002b] in C:\home\mk\work\frameworks\sqlite-net-extensions\SQLiteNetExtensions\Extensions\WriteOperations.cs:181
at SQLiteNetExtensions.Extensions.WriteOperations.InsertWithChildren (SQLite.SQLiteConnection conn, System.Object element, System.Boolean recursive) [0x00000] in C:\home\mk\work\frameworks\sqlite-net-extensions\SQLiteNetExtensions\Extensions\WriteOperations.cs:59
at SQLiteNetExtensionsAsync.Extensions.WriteOperations+<>c__DisplayClass1_0.<InsertWithChildrenAsync>b__0() [0x00013] in C:\home\mk\work\frameworks\sqlite-net-extensions\SQLiteNetExtensionsAsync-PCL\Extensions\WriteOperations.cs:55
at System.Threading.Tasks.Task.InnerInvoke() [0x0000f] in <d18287e1d683419a8ec3216fd78947b9>:0
at System.Threading.Tasks.Task.Execute() [0x00010] in <d18287e1d683419a8ec3216fd78947b9>:0
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() [0x0000c] in <d18287e1d683419a8ec3216fd78947b9>:0
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0003e] in <d18287e1d683419a8ec3216fd78947b9>:0
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in <d18287e1d683419a8ec3216fd78947b9>:0
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in <d18287e1d683419a8ec3216fd78947b9>:0
at System.Runtime.CompilerServices.TaskAwaiter.GetResult() [0x00000] in <d18287e1d683419a8ec3216fd78947b9>:0
at TestSQLite.Database+<StoreBasketAsync>d__5.MoveNext() [0x0021b] in C:\Users\some-user\Documents\Visual Studio 2015\Projects\TestSQLite\TestSQLite\TestSQLite\Database.cs:189
此外，我試圖在InsertWithChildrenAsync()使用recursive: true，但Pip也null。這裏是例子：
數據模型
public class Basket
{
private string number;
private List<Fruit> fruitList;
[PrimaryKey]
public string Number
{
get { return this.number; }
set { this.number = value; }
}
public string Name { get; set; }
[OneToMany(CascadeOperations = CascadeOperation.CascadeRead)]
public List<Fruit> FruitList
{
get { return this.fruitList; }
set { this.fruitList = value; }
}
public Basket()
{
}
}
public class Fruit
{
private string number;
private Pip pip;
[PrimaryKey]
public string Number
{
get { return this.number; }
set { this.number = value; }
}
public string Type { get; set;}
[ForeignKey(typeof(Pip))]
public string PipId { get; set; }
[OneToOne]
public Pip Pip
{
get { return this.pip; }
set { this.pip = value; }
}
[ForeignKey(typeof(Basket))]
public string BasketId { get; set; }
public Fruit()
{
}
}
public class Pip
{
private string number;
private string title;
[PrimaryKey]
public string Number
{
get { return this.number; }
set { this.number = value; }
}
public string Title
{
get { return this.title; }
set { this.title = value; }
}
public Pip()
{
}
}
數據庫操作
public class Database
{
private readonly SQLiteAsyncConnection database;
public Database(string databasePath)
{
this.database = new SQLiteAsyncConnection(databasePath);
this.database.CreateTableAsync<Basket>().Wait();
this.database.CreateTableAsync<Fruit>().Wait();
this.database.CreateTableAsync<Pip>().Wait();
}
public async Task<Basket> GetBasketAsync(string basketId)
{
try
{
var queryResult = await this.database.Table<Basket>().Where(b => b.Number == basketId).CountAsync();
if (queryResult > 0)
{
return await this.database.GetWithChildrenAsync<Basket>(basketId, true);
}
else
{
return null;
}
}
catch(Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.Message);
return null;
}
}
public async Task<Fruit> GetFruitAsync(string number)
{
try
{
var queryResult = await this.database.Table<Fruit>().Where(f => f.Number == number).CountAsync();
if (queryResult > 0)
{
return await this.database.GetWithChildrenAsync<Fruit>(number, true);
}
else
{
return null;
}
}
catch(Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.Message);
return null;
}
}
public async Task<Pip> GetPipAsync(string number)
{
try
{
var queryResult = await this.database.Table<Pip>().Where(p => p.Number == number).CountAsync();
if (queryResult > 0)
{
return await this.database.GetAsync<Pip>(number);
}
else
{
return null;
}
}
catch(Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.Message);
return null;
}
}
public async Task StoreBasketAsync(Basket basket)
{
if (basket == null)
return;
try
{
await this.StoreFruitListAsync(basket.FruitList);
var foundItem = await this.GetBasketAsync(basket.Number);
if (foundItem != null)
{
await this.database.UpdateWithChildrenAsync(basket);
}
else
{
await this.database.InsertWithChildrenAsync(basket);
}
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.Message);
}
}
public async Task StoreFruitListAsync(List<Fruit> fruitList)
{
if (fruitList == null || fruitList.Count == 0)
return;
try
{
foreach (Fruit fruit in fruitList)
{
await this.StorePipAsync(fruit.Pip);
var foundItem = await this.GetFruitAsync(fruit.Number);
if (foundItem != null)
{
await this.database.UpdateWithChildrenAsync(fruit);
}
else
{
await this.database.InsertWithChildrenAsync(fruit);
}
}
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.Message);
}
}
public async Task<int> StorePipAsync(Pip pip)
{
if (pip == null)
return 0;
try
{
var foundItem = await this.GetPipAsync(pip.Number);
if (foundItem != null)
{
return await this.database.UpdateAsync(pip);
}
else
{
return await this.database.InsertAsync(pip);
}
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.Message);
return 0;
}
}
}
測試用例
public MainPage()
{
InitializeComponent();
Pip pip = new Pip();
pip.Number = "4";
pip.Title = "pip from apple";
Fruit apple = new Fruit();
apple.Number = "1";
apple.Pip = pip;
Basket basket = new Basket();
basket.Number = "10";
basket.Name = "grandma";
basket.FruitList = new List<Fruit>() { apple };
this.basket = basket;
}
protected override async void OnAppearing()
{
base.OnAppearing();
await App.Database.StoreBasketAsync(this.basket);
Basket existingBasket = await App.Database.GetBasketAsync(this.basket.Number);
}
我使用的是最新的SQLiteNetExtensions.Async v2.0.0-alpha2 NuGet包。我如何正確檢索子元素Pip？