error using backingstore model library and explicit key property

Question

we are currently in the process of trying to get breeze and typescript working together... we are using angular and therefore plan on using breeze's "backingStore" model library... we don't plan on using ko or backbone...

    // configure to use the model library for Angular
    breeze.config.initializeAdapterInstance("modelLibrary", "backingStore", true);

we are defining all typescript entity properties at design time, including key properties... it appears that the "backingStore" implementation fails when the entity has a design time key property AND ALSO a navigation array property. specifically it appears line 4470 of breeze.debug.js is a problem:

     npValue.forEach(function(iv) {
     iv.setProperty(fkName, newValue);

if i understand things correctly, "npValue" should be an array that holds child entities... if this value is null, the above code fails... this code appears to run when breeze is loading entities client side as a result of a call to the server... and it only happens if the "key" property of the parent is defined explicitly in code inside the entity's constructor function. the call to "movePropsToBackingStore" appears to be deleting properties and then adding them back... when this is done for the key property, this problem arises...

anyway, is this a bug OR does breeze not support explicit definition of key properties? or is something else wrong? to reproduce this issue all you have to do is tweak the NoDb sample as follows:

    // configure to use the model library for Angular
    breeze.config.initializeAdapterInstance("modelLibrary", "backingStore", true);

    var TodoList = function () {
        this.title = "My todos";            
        this.todoListId = null; //explicitly define key prop
    };

thank you

Ward Ward · Accepted Answer · 2013-06-05T02:24:00

Short answer: initialize the primary key to 0, not null.

Long answer

I followed your repro advice and got an error as you said I would. Breeze complained that it didn't know how to fixup the primary keys after saving the TodoList.

Which is entirely expected ... because you set the TodoList primary key to null in your constructor. null is never a valid primary key value.

Now, as it happens, because keys are store generated, the server did save a new TodoList and returned it with the db-assigned primary key value. Breeze sees that the key changed and wants to fix-up other potential entity references to this TodoList. It will look for entities with the pre-save value. But it isn't prepared to search for the null value.

There is a Breeze bug here. We should never have let you assign null as the primary key. I'll file that bug and we'll fix it soon.

Meanwhile you should be fine using the value 0 instead of null.

Important: you must use the value 0. No other integer will do! The type default (0 is the integer type default) has special meaning to Breeze when the key is store-generated. It tells Breeze "for each create, replace this key with a new temporary key value, a placeholder until I save this entity."

But if you set it to null or any non-zero integer (say 1), Breeze assumes you want to initialize the key to this particular value. Therefore, every TodoList entity you create will have id=1. That may work the first create; it won't with the second because you'll have an id collision (no two entities of the same type in the same manager can have the same key).

So use 0. Hope this is clear.

BTW, the "NoDb" sample uses Knockout. I realize you are using Angular. I don't think that difference matters. The nature of the problem should be the same. I figure you will tell me if it does matter.

Are you defining metadata on the client?

I ask because the "NoDb" sample does and it is quite precise in how it defines the primary key column:

function addTodoListType(store) {
    store.addEntityType({
        shortName: "TodoList",
        namespace: "NoDb.Models",
        autoGeneratedKeyType: AutoGeneratedKeyType.Identity,
        dataProperties: {
            todoListId: { dataType: DataType.Int32, isNullable: false, isPartOfKey: true },
            title: { dataType: DataType.String, maxLength: 30, isNullable: false }
        },
        navigationProperties: {
            // returns a collection of TodoItems -- associates with TodoItem.TodoList
            todos: { entityTypeName: "TodoItem", isScalar: false, associationName: "TodoList_Items" }
        }
    });

Notice that it

identifies todoListId as the key by saying isPartOfKey: true
tells Breeze that the key for this type is store-generated: autoGeneratedKeyType: AutoGeneratedKeyType.Identity

My remarks above presuppose that your application is like "NoDb" in these respects, even if it uses Angular instead of Knockout for its model library.

error using backingstore model library and explicit key property

1 Answers

Long answer

Are you defining metadata on the client?