List Operations

Redis List is a simple string list, ordered by insertion order. Supports inserting and popping elements from both ends of the list.

LPush - Insert from Left

Insert Single Value

oRedis.LPush "mylist", "item1"

Insert Multiple Values

oRedis.LPush "mylist", "item2", "item3"

Note: Elements inserted using LPush appear at the beginning of the list.

RPush - Insert from Right

' Insert from right
oRedis.RPush "mylist", "item4"

Note: Elements inserted using RPush appear at the end of the list.

LPop - Pop from Left

Dim sValue As String
sValue = oRedis.LPop("mylist")
Debug.Print sValue  ' Output: leftmost element

RPop - Pop from Right

sValue = oRedis.RPop("mylist")
Debug.Print sValue  ' Output: rightmost element

LLen - Get List Length

Dim lLen As Long
lLen = oRedis.lLen("mylist")
Debug.Print "List length: " & lLen

LRange - Get Elements in Range

Get All Elements

Dim vItems As Variant
vItems = oRedis.LRange("mylist", 0, -1)

If IsArray(vItems) Then
    Dim i As Long
    For i = 0 To UBound(vItems)
        Debug.Print vItems(i)
    Next
End If

Get First 10 Elements

vItems = oRedis.LRange("mylist", 0, 9)

Get Specified Range Elements

' Get elements from 6th to 10th (index starts from 0)
vItems = oRedis.LRange("mylist", 5, 9)

Use Cases

1. Task Queue

Sub TaskQueue()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    Dim sQueue As String
    sQueue = "tasks:queue"

    ' Add tasks to queue
    oRedis.RPush sQueue, "Send email to user1"
    oRedis.RPush sQueue, "Generate report"
    oRedis.RPush sQueue, "Backup database"
    oRedis.RPush sQueue, "Clear cache"

    ' View queue length
    Debug.Print "Pending tasks: " & oRedis.lLen(sQueue)

    ' View all tasks
    Dim vTasks As Variant
    vTasks = oRedis.LRange(sQueue, 0, -1)

    Debug.Print vbCrLf & "All tasks:"
    Dim i As Long
    For i = 0 To UBound(vTasks)
        Debug.Print "  " & (i + 1) & ". " & vTasks(i)
    Next

    ' Process tasks (pop from left)
    Debug.Print vbCrLf & "Processing tasks..."
    While oRedis.lLen(sQueue) > 0
        Dim sTask As String
        sTask = oRedis.LPop(sQueue)
        Debug.Print "Processing: " & sTask
        Debug.Print "Remaining: " & oRedis.lLen(sQueue)
    Wend

    oRedis.DisConnect
End Sub

2. Message Queue

Sub MessageQueue()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    Dim sQueue As String
    sQueue = "messages:inbox"

    ' Send messages (producer)
    oRedis.RPush sQueue, "Message1: Hello"
    oRedis.RPush sQueue, "Message2: Redis is great"
    oRedis.RPush sQueue, "Message3: Learning"

    ' Receive messages (consumer)
    Debug.Print "New messages:"
    Dim lCount As Long
    lCount = oRedis.lLen(sQueue)

    For i = 1 To lCount
        Dim sMsg As String
        sMsg = oRedis.LPop(sQueue)
        Debug.Print "  " & sMsg
    Next

    oRedis.DisConnect
End Sub

3. History Records

Sub SearchHistory()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    Dim sUserId As String
    sUserId = "user:123:history"

    ' Add search records
    oRedis.LPush sUserId, "Redis tutorial"
    oRedis.LPush sUserId, "VB6 programming"
    oRedis.LPush sUserId, "Database design"

    ' Limit history records (keep only recent 10)
    While oRedis.lLen(sUserId) > 10
        oRedis.RPop sUserId
    Wend

    ' Get recent search records
    Dim vHistory As Variant
    vHistory = oRedis.LRange(sUserId, 0, 4)  ' Recent 5

    Debug.Print "Recent search records:"
    Dim i As Long
    If IsArray(vHistory) Then
        For i = 0 To UBound(vHistory)
            Debug.Print "  " & (i + 1) & ". " & vHistory(i)
        Next
    End If

    oRedis.DisConnect
End Sub

4. Recent Activity

Sub RecentActivity()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    Dim sKey As String
    sKey = "activity:recent"

    ' Add activities
    oRedis.LPush sKey, "User Zhang San published new article"
    oRedis.LPush sKey, "User Li Si commented on article"
    oRedis.LPush sKey, "User Wang Wu liked post"
    oRedis.LPush sKey, "User Zhao Liu followed new user"

    ' Keep only latest 20 activities
    While oRedis.lLen(sKey) > 20
        oRedis.RPop sKey
    Wend

    ' Show recent activities
    Dim vActivities As Variant
    vActivities = oRedis.LRange(sKey, 0, 9)

    Debug.Print "Recent activities:"
    Dim i As Long
    If IsArray(vActivities) Then
        For i = 0 To UBound(vActivities)
            Debug.Print "  " & (i + 1) & ". " & vActivities(i)
        Next
    End If

    oRedis.DisConnect
End Sub

5. Stack (LIFO)

Sub StackExample()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    Dim sStack As String
    sStack = "stack:operations"

    ' Push operations
    Debug.Print "Push operations:"
    oRedis.LPush sStack, "Element A"
    Debug.Print "  Pushed: Element A"

    oRedis.LPush sStack, "Element B"
    Debug.Print "  Pushed: Element B"

    oRedis.LPush sStack, "Element C"
    Debug.Print "  Pushed: Element C"

    Debug.Print "Stack depth: " & oRedis.lLen(sStack)

    ' Pop operations
    Debug.Print vbCrLf & "Pop operations:"
    While oRedis.lLen(sStack) > 0
        Dim sItem As String
        sItem = oRedis.LPop(sStack)
        Debug.Print "  Popped: " & sItem
        Debug.Print "  Remaining: " & oRedis.lLen(sStack)
    Wend

    oRedis.DisConnect
End Sub

6. Queue (FIFO)

Sub QueueExample()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    Dim sQueue As String
    sQueue = "queue:customers"

    ' Enqueue operations
    Debug.Print "Enqueue operations:"
    oRedis.RPush sQueue, "Customer A"
    Debug.Print "  Enqueued: Customer A"

    oRedis.RPush sQueue, "Customer B"
    Debug.Print "  Enqueued: Customer B"

    oRedis.RPush sQueue, "Customer C"
    Debug.Print "  Enqueued: Customer C"

    Debug.Print "Queue length: " & oRedis.lLen(sQueue)

    ' Dequeue operations
    Debug.Print vbCrLf & "Dequeue operations:"
    While oRedis.lLen(sQueue) > 0
        Dim sCustomer As String
        sCustomer = oRedis.LPop(sQueue)
        Debug.Print "  Serving: " & sCustomer
        Debug.Print "  Waiting: " & oRedis.lLen(sQueue)
    Wend

    oRedis.DisConnect
End Sub

Complete Example

Sub Example_ListOperations()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then
        Debug.Print "Connection failed: " & oRedis.LastError
        Exit Sub
    End If

    ' Clear existing list
    oRedis.Del "tasks"

    ' Add tasks
    oRedis.RPush "tasks", "Task1"
    oRedis.RPush "tasks", "Task2"
    oRedis.RPush "tasks", "Task3"
    oRedis.RPush "tasks", "Task4"
    oRedis.RPush "tasks", "Task5"

    ' Get list length
    Debug.Print "Task list length: " & oRedis.lLen("tasks")

    ' Get all tasks
    Dim vTasks As Variant
    vTasks = oRedis.LRange("tasks", 0, -1)

    Debug.Print vbCrLf & "All tasks:"
    Dim i As Long
    For i = 0 To UBound(vTasks)
        Debug.Print "  " & (i + 1) & ". " & vTasks(i)
    Next

    ' Process first task
    Debug.Print vbCrLf & "Processing task: " & oRedis.LPop("tasks")
    Debug.Print "Remaining tasks: " & oRedis.lLen("tasks")

    ' Add new task to front
    oRedis.LPush "tasks", "Urgent task"

    ' View updated list
    vTasks = oRedis.LRange("tasks", 0, -1)
    Debug.Print vbCrLf & "Updated task list:"
    If IsArray(vTasks) Then
        For i = 0 To UBound(vTasks)
            Debug.Print "  " & (i + 1) & ". " & vTasks(i)
        Next
    End If

    oRedis.DisConnect
End Sub

List Operations Summary

Operation	Method	Description
Left insert	LPush	Insert from list beginning
Right insert	RPush	Insert from list end
Left pop	LPop	Pop from list beginning
Right pop	RPop	Pop from list end
Get length	LLen	Get number of list elements
Get range	LRange	Get elements in specified range

Usage Recommendations

1. Task Queue: Use RPush + LPop for FIFO
2. Stack: Use LPush + LPop for LIFO
3. Limit Size: Use RPush + RPop or LPush + RPop to control list length
4. History Records: Use LPush to add new records, LRANGE to get recent records