Class MetaMaker

source code

                   object --+                    
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 base.structure.StructureBase --+                
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                   object --+   |                
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           base.common.Parser --+                
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base.structure.ParseableStructure --+            
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             base.structure.Structure --+        
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                           object --+   |        
                                    |   |        
      base.structure.RestrictionMixin --+        
                                        |        
                   rscdef.procdef.ProcDef --+    
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                       rscdef.procdef.ProcApp --+
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                                               MetaMaker

A procedure application that generates metadata for datalink services.

The code must be generators (i.e., use yield statements) producing either svcs.InputKeys or protocols.datalink.LinkDef instances.

metaMaker see the data descriptor of the input data under the name descriptor.

The data attribute of the descriptor is always None for metaMakers, so you cannot use anything given there.

Within MetaMakers' code, you can access InputKey, Values, Option, and LinkDef without qualification, and there's the MS function to build structures. Hence, a metaMaker returning an InputKey could look like this:

       <metaMaker>
               <code>
                       yield MS(InputKey, name="format", type="text",
                               description="Output format desired",
                               values=MS(Values,
                                       options=[MS(Option, content_=descriptor.mime),
                                               MS(Option, content_="text/plain")]))
               </code>
       </metaMaker>

(of course, you should give more metadata -- ucds, better description, etc) in production).

It's ok to yield None; this will suppress a Datalink and is convenient when some component further down figures out that a link doesn't exist (e.g., because a file isn't there). Note that in many cases, it's more helpful to client components to handle such situations by yielding a DatalinkFault.NotFoundFault.

In addition to the usual names available to ProcApps, meta makers have:

• MS -- function to make DaCHS structures
• InputKey -- the class to make for input parameters
• Values -- the class to make for input parameters' values attributes
• Options -- used by Values
• LinkDef -- a class to define further links within datalink services.
• DatalinkFault -- a container of datalink error generators
• soda -- the soda module.