To use a CICS® resource, such as a file or program, you must first create an appropriate object and then call methods on the object.
When you create a resource object you create a representation of the actual CICS resource (such as a file or program). You do not create the CICS resource; the object is simply the application's view of the resource. The same is true of destroying objects.
You are recommended to use an accompanying resource identification object when creating a resource object. For example:
IccFileId id("XYZ123");
IccFile file(id);
This allows the C++ compiler to protect you against doing something wrong such as:
IccDataQueueId id("WXYZ");
IccFile file(id); //gives error at compile time
The alternative of using the text name of the resource when creating the object is also permitted:
IccFile file("XYZ123");
Many resource classes, such as IccFile, can be used to create multiple resource objects within a single program:
IccFileId id1("File1");
IccFileId id2("File2");
IccFile file1(id1);
IccFile file2(id2);
However, some resource classes are designed to allow the programmer to create only one instance of the class; these are called singleton classes. The following Foundation Classes are singleton:
Any attempt to create more than one object of a singleton class results in an error - a C++ exception is thrown.
A class method, instance, is provided for each of these singleton classes, which returns a pointer to the requested object and creates one if it does not already exist. For example:
IccControl* pControl = IccControl::instance();
Any of the public methods can be called on an object of that class. For example:
IccTempStoreId id("TEMP1234");
IccTempStore temp(id);
temp.writeItem("Hello TEMP1234");
Method writeItem writes the contents of the string it is passed ("Hello TEMP1234") to the CICS Temporary Storage queue "TEMP1234".
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