String Operations

Redis String is the simplest data type, capable of storing strings, integers, or floating-point numbers.

Set_ - Set Key-Value

Basic Setting

oRedis.Set_ "name", "Zhang San"
oRedis.Set_ "age", "25"
oRedis.Set_ "city", "Beijing"

Set with Expiration

' Set expiration time (seconds)
oRedis.Set_ "session", "abc123", , 3600  ' Expire in 1 hour

' Set expiration time (milliseconds)
oRedis.Set_ "token", "xyz789", , 60000  ' Expire in 1 minute

Get_ - Get Key Value

Dim sValue As String
sValue = oRedis.Get_("name")
Debug.Print sValue  ' Output: Zhang San

Incr - Increment

Increment the numeric value in the key by 1:

' Initialize counter
oRedis.Set_ "counter", "10"

' Increment
Dim lValue As Long
lValue = oRedis.Incr("counter")
Debug.Print lValue  ' Output: 11

' Increment again
lValue = oRedis.Incr("counter")
Debug.Print lValue  ' Output: 12

Use Cases:

• Counters
• ID generation
• Access statistics

Decr - Decrement

Decrement the numeric value in the key by 1:

' Decrement
lValue = oRedis.Decr("counter")
Debug.Print lValue  ' Output: 10

MGet - Batch Get

Get values of multiple keys simultaneously:

' Get multiple keys at once
Dim vValues As Variant
vValues = oRedis.MGet("name", "age", "city")

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

Return Value Explanation:

• Returns corresponding value if key exists
• Returns empty string if key does not exist

MSet - Batch Set

Batch set multiple key-value pairs:

' Batch set key-value pairs
oRedis.MSet "name", "Li Si", "age", "25", "city", "Beijing"

Use Cases

1. User Session Management

Sub UserSession()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    Dim sUserId As String
    sUserId = "user:12345"

    ' Create session
    oRedis.Set_ sUserId & ":name", "Zhang San"
    oRedis.Set_ sUserId & ":email", "zhangsan@example.com"
    oRedis.Set_ sUserId & ":login_time", CStr(Now())

    ' Set session expiration time to 30 minutes
    oRedis.Expire sUserId & ":name", 1800
    oRedis.Expire sUserId & ":email", 1800
    oRedis.Expire sUserId & ":login_time", 1800

    ' Get session information
    Dim vSession As Variant
    vSession = oRedis.MGet(sUserId & ":name", sUserId & ":email")
    If IsArray(vSession) Then
        Debug.Print "User: " & vSession(0)
        Debug.Print "Email: " & vSession(1)
        Debug.Print "Remaining time: " & oRedis.TTL(sUserId & ":name") & " seconds"
    End If

    oRedis.DisConnect
End Sub

2. Counter

Sub CounterExample()
    Dim oRedis As New cRedisClient

    If Not oRedis.Connect() Then Exit Sub

    ' Page visit count
    Dim sPage As String
    sPage = "page:/home"

    ' Increment visit count
    Dim lCount As Long
    lCount = oRedis.Incr(sPage)
    Debug.Print "Page visit count: " & lCount

    ' Article like count
    oRedis.Incr "article:1001:likes"
    oRedis.Incr "article:1001:likes"
    oRedis.Incr "article:1001:likes"

    Debug.Print "Article likes: " & oRedis.Get_("article:1001:likes")

    oRedis.DisConnect
End Sub

3. Distributed ID Generation

Function GenerateId(ByVal sPrefix As String) As String
    Static oRedis As cRedisClient

    If oRedis Is Nothing Then
        Set oRedis = New cRedisClient
        If Not oRedis.Connect() Then
            Debug.Print "Connection failed"
            Exit Function
        End If
    End If

    Dim lId As Long
    lId = oRedis.Incr("id:" & sPrefix)

    GenerateId = sPrefix & ":" & lId
End Function

Sub TestIdGeneration()
    Debug.Print GenerateId("order")    ' Output: order:1
    Debug.Print GenerateId("order")    ' Output: order:2
    Debug.Print GenerateId("user")     ' Output: user:1
    Debug.Print GenerateId("order")    ' Output: order:3
End Sub

4. Rate Limiter

Function RateLimit(ByVal sUserId As String, ByVal lLimit As Long) As Boolean
    Static oRedis As cRedisClient

    If oRedis Is Nothing Then
        Set oRedis = New cRedisClient
        If Not oRedis.Connect() Then
            Exit Function
        End If
    End If

    Dim sKey As String
    sKey = "ratelimit:" & sUserId

    Dim lCount As Long
    lCount = oRedis.Incr(sKey)

    ' Set expiration time on first request (1 minute)
    If lCount = 1 Then
        oRedis.Expire sKey, 60
    End If

    ' Check if limit exceeded
    If lCount > lLimit Then
        Debug.Print "Limit exceeded, current requests: " & lCount
        RateLimit = False
    Else
        RateLimit = True
    End If
End Function

Sub TestRateLimit()
    Dim i As Long
    For i = 1 To 12
        Debug.Print "Request " & i & ": " & IIf(RateLimit("user123", 10), "Allowed", "Denied")
    Next i
End Sub

5. Cache Management

Function GetCachedData(ByVal sKey As String, ByVal sDefault As String) As String
    Static oRedis As cRedisClient

    If oRedis Is Nothing Then
        Set oRedis = New cRedisClient
        oRedis.Connect
    End If

    Dim sValue As String
    sValue = oRedis.Get_(sKey)

    If sValue = "" Then
        ' Cache miss, return default value
        GetCachedData = sDefault

        ' Store default value in cache with 1 hour expiration
        oRedis.Set_ sKey, sDefault, , 3600
    Else
        GetCachedData = sValue
    End If
End Function

Sub TestCache()
    Debug.Print "First fetch: " & GetCachedData("config:appname", "MyApp")
    Debug.Print "Second fetch: " & GetCachedData("config:appname", "MyApp")
End Sub

Complete Example

Sub Example_StringOperations()
    Dim oRedis As New cRedisClient

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

    ' Set values
    oRedis.Set_ "name", "Zhang San"
    oRedis.Set_ "age", "25"

    ' Get values
    Debug.Print "Name: " & oRedis.Get_("name")
    Debug.Print "Age: " & oRedis.Get_("age")

    ' Set expiration time
    oRedis.Expire "name", 300

    ' Check remaining time
    Debug.Print "name remaining TTL: " & oRedis.TTL("name") & " seconds"

    ' Counter example
    oRedis.Set_ "counter", "10"
    Debug.Print "Initial value: " & oRedis.Get_("counter")
    Debug.Print "After increment: " & oRedis.Incr("counter")
    Debug.Print "Increment again: " & oRedis.Incr("counter")
    Debug.Print "After decrement: " & oRedis.Decr("counter")

    ' Batch operations
    oRedis.MSet "user:1", "Zhang San", "user:2", "Li Si", "user:3", "Wang Wu"
    Dim vUsers As Variant
    vUsers = oRedis.MGet("user:1", "user:2", "user:3")

    Debug.Print vbCrLf & "Batch fetch results:"
    Dim i As Long
    If IsArray(vUsers) Then
        For i = 0 To UBound(vUsers)
            Debug.Print "  User" & (i + 1) & ": " & vUsers(i)
        Next
    End If

    oRedis.DisConnect
End Sub