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ValueMap and Value Qualifiers

  • Článek

A value map is an array linked to a property with the Value and ValueMap qualifiers.

The property acts as an index into the array, holding a value that represents one of the values in the array. Using MOF code, you can have the following types of value maps:

  • Array mapping to an integer.

    You can define an array with the Value qualifier and link the array directly to an integer property, as shown in the following example:

    [Values {"OK", "Error", "Degraded", "Unknown"}, Read]
sint32 Status;

    In this example, the Status property value is an index into the string array defined by Value. The property can only take on values that correspond to the ordinal positions in the Value array minus 1. For example, setting Status to "1" maps to the "Error" value. The index property can take only values that correspond to positions in the Value array. For example, if the array has 10 entries, the index property can story 0 through 9, not 30 or 177.

  • Array mapping to another array mapping to an integer.

    If you wish to create an index that does not use an ordinal system of counting, use the ValueMap qualifier. The ValueMap qualifier sets up another array that holds an arbitrary index numbering system, as shown in the following example:

    [ValueMap {"1", "3", "99", "0"}, 
 Values {"OK", "Error", "Degraded", "Unknown"}, Read]
sint32 Status;

    Although you must place the values of ValueMap in quotations, WMI considers the values integers. Therefore, In this example you can set the Status property to an integer in the ValueMap set: 1, 3, 99, or 0. WMI maps each integer from an ordinal position in the ValueMap string array to a corresponding position in the Value array. For example, setting Status to 0 maps to "Unknown".

  • Array mapping to another array mapping to a string.

    If you do not want to use an integer to index your array, you can instead use a string to hold one of the possible values in your array. To do so, you must define both a Value and ValueMap array that both contain strings, as shown in the following example:

    [ValueMap {"OK", "Error", "Degraded", "Unknown"}, 
 Values {"OK", "Error", "Degraded", "Unknown"}, Read]
string Status;

    With a string property, the actual allowable values of the property are the entries in the ValueMap array. For example, you can set Status to "OK" or "Unknown".

It is up to the application to take advantage of mappings in a useful way. It is up to the provider to enforce a legal range of values.

Remarks

In deciding whether to use the ValueMap/Value or BitMap/BitValues qualifiers, determine whether any of the values being indicated could occur concurrently. If multiple concurrent values can exist, you must use BitMap/BitValues. If all the values are mutually exclusive, you should use the ValueMap/Value qualifiers.

BitMap and BitValues