New (Dataset constructor): Difference between revisions
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<tr><th><var>%(Dataset)</var></th> | <tr><th><var>%(Dataset)</var></th> | ||
<td>The class name in parentheses denotes a <var>[[Notation conventions for methods#Constructors|Constructor]]</var>. | <td>The class name in parentheses denotes a <var>[[Notation conventions for methods#Constructors|Constructor]]</var>. See [[#Usage notes|"Usage notes"]], below, for more information about invoking a <var>Dataset</var> <var>Constructor</var>. | ||
</td></tr> | </td></tr> | ||
<tr><th>dsname</th> | <tr><th>dsname</th> | ||
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==Usage notes== | ==Usage notes== | ||
<ul> | <ul> | ||
<li>As described in [[Object variables#Using New or other Constructors|"Using New or other Constructors"]], <var>New</var> can be invoked with no object, with an explicit class name, or with an object variable in the class, even if that object is <var>Null</var>:<p class="code">%dataset = new | |||
%dataset = %(Dataset):new | |||
%dataset = %dataset:new | |||
</p> | |||
<li>The dataset name must be 8 characters or shorter and cannot contain | <li>The dataset name must be 8 characters or shorter and cannot contain | ||
leading or intermediate blanks. | leading or intermediate blanks. | ||
Revision as of 21:27, 27 July 2011
Create a new dataset object (Dataset class)
This constructor creates a new instance of a Dataset object.
Syntax
%dataset = [%(Dataset):]New( string)
Syntax terms
| %dataset | A variable to receive a reference to the newly created
Dataset object. |
|---|---|
| %(Dataset) | The class name in parentheses denotes a Constructor. See "Usage notes", below, for more information about invoking a Dataset Constructor. |
| dsname | The name of the dataset or stream to be associated with the Dataset
object. This is a required argument. |
Usage notes
- As described in "Using New or other Constructors", New can be invoked with no object, with an explicit class name, or with an object variable in the class, even if that object is Null:
%dataset = new %dataset = %(Dataset):new %dataset = %dataset:new
- The dataset name must be 8 characters or shorter and cannot contain leading or intermediate blanks. It also cannot contain other characters not allowed in dataset or stream names. Failure to conform to these rules results in request cancellation.
- The New constructor does not validate that the Dataset is allocated or the stream defined. This is because a dataset can be allocated or freed before it is actually opened, or a stream could be defined or deleted before it is opened. As such, checking dataset or stream existence at New time wouldn't be a reliable check, so it is not done.