HRead (Function)

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Records read
Looping through a data file
Memos
Locks
Miscellaneous

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HRead (Function)

In french: HLit

Not available with this kind of connection

Reads a record in a data file according to a given record number. This read mode is called "Direct access". The record read is loaded in memory. HState is used to find out the record status (active, crossed or deleted).

In most cases, HRead is used to position in the data file in order to perform a read loop by specifying the record number.

Several cases may occur after the call to HRead:

the specified record number does not exist (greater than the total number of records or negative): no reading is performed and HOut returns True.
the specified record number does not exist anymore (crossed record, deleted record, ...): no read operation is performed and HOut returns False.
Use HState to find out the record status.
the data file is empty: HOut returns True.
the function tries to lock a record that is already locked in read-only: HErrorLock returns True and HOut returns True.

This function can be used with the data files (indexed or not) and with the HFSQL views.

Example

// Sequential iteration to display the name of all customers
i is int
FOR i = 1 _TO_ HNbRec(Customer, hStateAll)
HRead(Customer, i)
IF HState() = hStateActive THEN
Info("Customer name: " + Customer.Name)
END
END

Syntax

<Result> = HRead([<Data file> [, <Record number> [, <Options>]]])

<Result>: Boolean

True if the record was read,
False if an error occurred (lock, end of data file, etc.): the record is not read. HError is used to identify the error.

<Data file>: Optional character string

Name of the HFSQL data file, view or query used.
If this parameter is an empty string (""), HRead manipulates the last data file used by the last HFSQL function (function starting with "H").

<Record number>: Optional integer

Number of the record to read.
If this parameter is not specified (or is equal to 0 or to the hCurrentRecNum constant), HRead will read the current record.
HRead reads the current record only. You cannot specify a record number other than the current one. To specify the current record number, use the hCurrentRecNum constant.

<Options>: Optional constant

Configures the lock set on the record read by HRead:
hLockNo No lock: the record can be read or modified by another application during the reading.
hLockReadWrite Lock in read/write mode: the record currently read cannot be read or modified by another application.
hLockWrite Lock in write mode: the record currently read can be read by another application but it cannot be modified by another application.
The lock options are ignored. Use locking functions (HLockRecNum) kept for backward compatibility.
The lock options will have no effect if the locks are not supported by the OLE DB provider or by the Native Connector.

Remarks

Records read

HRead is the only function that can be used to access a crossed or deleted record. If the record is deleted, the content of the record is not valid anymore.

Looping through a data file

HRead cannot be used to continue an iteration started by HReadFirst, HReadNext.

Memos

The memos associated with the record can be automatically read (or not) when reading the record. HSetMemo is used to customize this automatic read operation.

If the memos are supported, the associated text memos are read when the record is read. The binary memos are read only when they are explicitly used (HExtractMemo).

Locks

By default (<Options> not specified), the record is not locked.

If a lock is requested (hLockWrite or hLockReadWrite constant), the record will be read only if this record is not already locked.

The lock options will have no effect if the locks are not supported by the OLE DB provider or by the Native Connector.

Miscellaneous

The result of HFound must be ignored (HFound must be used for the searches performed by HReadSeekFirst and HReadSeekLast).
HRecNum returns the current record number. The first record found in the data file is record #1.
This function replaces HReadLock and HReadNoLock, which were kept for compatibility with WINDEV 5.5.

Component: wd300hf.dll