Reading Data from a View

The following syntax is used to read the value of a field in a view:

 

x = view_name.field_name

 

This syntax reads the value of field_name for the current record in view_name. If there is no current record, execution of this statement causes an error.

 

Here is a short sample macro that loops over each state in a dBASE file, reading the name and population of each one and displaying it in a message box:

 

// First, create the view

view = OpenTable("State Data", "DBASE", {"c:\\dbf\\states.dbf",} )

// Create a view|set for reading all records

view_set = view + "|"

rec = GetFirstRecord(view_set, null)

while rec <> null do

     // read the state name and population

     name = view.Name

     pop = view.Population

 

     // Display the information

     str = "The population of " + name + " is " + String(pop)

     ShowMessage(str)

 

     // Go on to the next state

     rec = GetNextRecord(view_set, null, null)

     end

 

Note that the view_name must be a variable name and not a literal string. That is:

 

// This won't work...

name = States.Name

 

// Neither will this...

name = "States".Name

 

// This, on the other hand, works just fine...

vw = "States"

name = vw.Name

 

If the name of the field you want to read is stored in a variable, you must put parentheses around the variable, as follows:

 

// Here are two ways to read the state name...

vw = "States"

fld = "Name"

 

// These two statements do the same thing...

name = vw.Name

name = vw.(fld)

 

// I am going to read the values of three fields...

fld_names = {"Name", "Population", "Income"}

vw = "States"

 

// Read the three field values...

name = vw.(fld_names[1])

pop = vw.(fld_names[2])

inc = vw.(fld_names[3])

 

In addition to the above syntax, the following GISDK functions can be used to read data from a view:

 

GISDK Function	Summary
GetEditorValues()	Reads a two-dimensional array of values from an editor window
GetFieldValues()	Reads the values of one or more fields in any number of views
GetRecordValues()	Reads the values of one or more fields for a record in a view
GetRecordsValues()	Reads the values of one or more fields for a group of records in a view
SampleValues()	Samples the values of the specified field and returns the specified number of unique values