Databases
StackOverflow2013
Postsdbo
POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
    primarykey
    data
    text
    <p>I have a Delphi 6 class object that contains an array of 30 Variants, each of which is exposed via a different indexed property. For example:</p> <pre><code>property responseCode: integer Index 7 read getIndexedProperty_integer write setIndexedProperty_integer; </code></pre> <p>I did this to make using the array of Variants easier (helps the IDE's auto-complete) and to provide type safety. It works fine but now I have a wrinkle. The array of Variants are initialized to NULL when the class that wraps it is constructed, so I can tell if a particular variant has ever been instantiated with a value. A consequence of this is if only some of the Variants are instantiated (given valid values), any attempt to access a property that currently represents a NULL Variant will cause a Variant conversion error when Delphi tries to convert the variant to the type declared by the indexed property.</p> <p>I would much rather not declare an "isValid" property for each indexed property. I was wondering if there was a way to use the TypeInfo library to get the raw value of the underlying Variant without having to access the indexed property directly and thus triggering the conversion Exception. Then I could write code like (using the example property above):</p> <pre><code>isValidProperty(responseCode); </code></pre> <p>and that function would return TRUE if the Variant underlying the responseCode property is not NULL and FALSE if it is.</p> <p>I know I can walk the PPropList property list for the class and access the properties by name, but then I would have to use code like:</p> <pre><code>isValidProperty('responseCode'); </code></pre> <p>and pass the property name in string form instead of passing in the property directly like the first isValidProperty() above. Is there a way to do this?</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USRobert Oschler
    1. USRobert Oschler
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI doubt which you can do that, because the rtti doesn't know nothing about the code to assign the variant value to the integer property located in the `getIndexedProperty_integer` method , so the underlying variant value can't be accessed in that way. my recomendation is which you modify the code of each getter method adding the `VarIsNull` function to check the variant values.
      singulars
      1. POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
      1. USRRUZ
    2. COWe're doing something similar, but the accessor is returning a default value in the case that the Variant is Null.
      singulars
      1. POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
      1. USJens Mühlenhoff
    3. COWhy does using variants "provide type safety"? It gives the opposite in a sense: you have the problem here of not knowing the underlying type and only being able to find out at runtime. Wouldn't a better solution be to have an array of integers, or if each of the 30 has a different type, explicitly have different properties?
      singulars
      1. POHow can I get the underlying raw Variant value of a Delphi 6 indexed property that accesses that Variant?
      1. USDavid M
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload