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><A
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>3.2. Objects of type hk_dsdatavisible - the class hk_column</H1
><P
>For the next example, create a form, set a datasource, create a lineedit field and connect it to a column of the datasource (for details see the
knoda tutorial at http://hk-classes.sourceforge.net/tutorials.</P
><P
>A lineeditfield is of type <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>hk_dsdatavisible</I
></SPAN
>. hk_dsdatavisible inherits from hk_dsvisible.
The most important method of hk_dsdatavisible is <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>column()</I
></SPAN
>. This method returns a class of type hk_column, representing
a specific column of a table.</P
><P
><DIV
CLASS="FIGURE"
><HR><A
NAME="AEN228"
></A
><P
><B
>Figure 3-4. hk_column data methods</B
></P
><A
NAME="AEN230"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><UL
><LI
STYLE="list-style-type: disc"
><P
>set_asstring(value): lets you set a new value for this object</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>asstring(): returns the current value</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>set_asdouble(): lets you set a new value for this object</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>asdouble(): returns the current value as a double value</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>set_asinteger(): lets you set a new value for this object</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>asinteger(): returns the current value as a integer value</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>is_readonly(): returns true if this column is read-only; if data can be changed it returns false</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>unsigned int find(from_rownumber,to_rownumber,searchtext,bool wholephrase=false,bool casesensitive=false,bool backwards=false);</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>unsigned int find(searchtext,bool wholephrase=false,bool casesensitive=false,bool backwards=false);</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>hk_datasource* datasource()</P
></LI
></UL
></BLOCKQUOTE
><HR></DIV
>
<DIV
CLASS="FIGURE"
><HR><A
NAME="AEN252"
></A
><P
><B
>Figure 3-5. hk_column type methods</B
></P
><A
NAME="AEN254"
></A
><BLOCKQUOTE
CLASS="BLOCKQUOTE"
><UL
><LI
STYLE="list-style-type: disc"
><P
>hk_string name(void);</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>void set_name(const hk_string& n): sets the column name</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>enum_columntype {textcolumn,auto_inccolumn,smallintegercolumn,integercolumn,smallfloatingcolumn,floatingcolumn,datecolumn,datetimecolumn,timecolumn,timestampcolumn,binarycolumn,memocolumn,boolcolumn,othercolumn}</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>columntype(): returns the type of the column</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>size(): returns the column size (e.g. if this column was created as CHAR(10) it will return 10)</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>bool is_primary(void): returns true if this column is part of a primary key</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>bool set_primary(bool i)</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>bool is_notnull(void);</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>bool set_notnull(bool i): if true the column needs a value</P
></LI
></UL
></BLOCKQUOTE
><HR></DIV
>
<DIV
CLASS="EXAMPLE"
><HR><A
NAME="AEN274"
></A
><P
><B
>Example 3-3. Read data</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> 1 col=hk_this.datasource().column_by_name("name")
2 hk_this.show_warningmessage(col.asstring())</PRE
></TD
></TR
></TABLE
><HR></DIV
>
<DIV
CLASS="EXAMPLE"
><HR><A
NAME="AEN277"
></A
><P
><B
>Example 3-4. Write data</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> 1 col=hk_this.datasource().column_by_name("name")
2 col.set_asstring("my new value")</PRE
></TD
></TR
></TABLE
><HR></DIV
>
This changes the value of the current column. The data is saved either when
<UL
><LI
STYLE="list-style-type: disc"
><P
>the row position changes (e.g. by calling hk_datasource.goto_row())</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>the datasource is disabled (e.g. by calling hk_datasource.disable())</P
></LI
><LI
STYLE="list-style-type: disc"
><P
>the changes are manually stored by calling hk_datasource.store_changed_data()</P
></LI
></UL
>
<DIV
CLASS="EXAMPLE"
><HR><A
NAME="AEN287"
></A
><P
><B
>Example 3-5. Search data</B
></P
><TABLE
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> 1 col=hk_this.datasource().column_by_name("name")
2 result=col.find("Schiller")
3 if result > hk_this.datasource().max_rows():
4 hk_this.show_warningmessage("value not found")
5 else:
6 hk_this.show_warningmessage("Value found at row position: "+str(result))</PRE
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