Problem in using TBuffDataSet
lazarus / 31-LCL

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kjteng · 2014-01-26 06:50

I thought TBuffdataset works like TRXmemoData since the methods look
similar. However,  I keep getting index out of bound error and the
fields count property is always zero even though there are 3 entries
in the  fieldDef property. Please help.

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tatamata · 2014-01-26 07:25

Hi. In TBfuDataset, fields are not automatically created from
FieldDefs, you have to create it by executing CreateDataset method, in
code.
Also, you have to set MaxIndexes count property to some reasonable
Integer value.

However, instead of using TBufDataset, you might try zmsql package
(current version attached), (see:
http://wiki.lazarus.freepascal.org/ZMSQL) which contains
ZMQueryDataset component that encapsulates TBufDataset with all it's
properties,  in user-friendly way, adding some useful methods and
properties that saves you from coding details.

For instance, you can create dynamic or persistent fields in design-
time, by  properties DynamicFieldsCreated, PersistentFieldsCreated,
MemoryDatasetOpened.
Also, you can directly open a .csv table by TableName and TableLoaded
properties, setting "database" folder in ZMConnection
property/component.
You can even execute simple SQL queries on CSV tables by properties
SQL, Parameters, QueryExecuted.
And, even more, you can set master/detail filtration between
zmquerydatasets by setting properties MasterDataSource, MasterFields,
MasterDetailFiltration, as well as master/slave referential integrity
between datasets (referential insert, update, delete) by setting
ZMReferentialKey property/component.