birt barcode4j REDO AND UNDO in Objective-C

Insert data matrix barcodes in Objective-C REDO AND UNDO

It s very easy to reach erroneous conclusions based on previous experience. Let me give you an example. Working a lot with Oracle Real Application Clusters (RAC), I learned pretty much all the common symptoms and causes for node evictions in an Oracle RAC cluster. I knew there are a few components that cause node eviction, and I could always quickly determine by running Oracle 10g Release 2 on Linux (let s be specific) that it s one of three Clusterware components that can evict a node: the CSSD daemon, the OCLSOMON daemon, and the hangcheck-timer module (which is actually part of the Linux operating system).

Figure 4-5. The swap_values method contains a reference pair to main s copy of p as well as a local integer variable to hold a temporary value.

The following code shows two method declarations. The first returns a value of type int. The second doesn t return a value. Return type int GetHour() { ... } void DisplayHour() { ... } No value is returned. A method that declares a return type must return a value from the method by using the following form of the return statement, which includes an expression after the keyword return. Every path through the method must end with a return statement of this form. return Expression; Evaluates to a value of the return type // Return a value.

The if and else keywords are used to define an if statement, which will perform a block of statements when a condition evaluates to the bool value true.

On-demand loading is the mechanism to load objects as they are required by the application by making separate query requests to the data source for each object. The main objective for such a mechanism is to dedicate memory resources only when necessary by loading and instantiating an object only at the point when it is absolutely needed. This approach is advisable when you need to load the data for a few entities and the volume of the data is large. To facilitate loading on demand, the DataServiceContext class has a BeginLoadProperty method, which follows the same asynchronous model where you specify the source entity, the name of the property, and a callback, as shown in the BeginLoadProperty method signature here: public IAsyncResult BeginLoadProperty( Object entity, string propertyName, AsyncCallback callback, Object state ) So let s implement this approach in our example by adding the following line of code in the BookDataGrid_SelectionChanged method. //Explicit loading (Lazy loading) using BeginLoadPropety context.BeginLoadProperty(currentBook , "BookDetails", PropertyLoadCompleted, null); The callback method PropertyLoadCompleted is as follows: private void PropertyLoadCompleted(IAsyncResult result) { context.EndLoadProperty(result); //Getting reference to current selected book Book currentBook = BookDataGrid.SelectedItem as Book; if (currentBook == null) return; var query = (from bd in currentBook.BookDetails select bd); BookDetailsDataGrid.ItemsSource = query.ToList(); } So, as per the code snippet, once the EndLoadProperty is called, the property has been properly loaded with the related entity, so we can access the related entity BookDetail through the navigation property BookDetails to bind to our BookDetailsDataGrid control.