vba 中的循环和退出循环-ag捕鱼王app官网

计算机编程中的循环非常重要。它们允许用最少的代码行执行重复性任务。取决于要执行的任务，计算机中对循环的需求有几个原因。

尽管它们非常强大，但它们在上下文和语法上都很简单。

在 vba 中，可以使用三个循环。

vba for 循环

语法：

for [ counter ] = [start] to [end]  step [ step ]
    [ statements ]
    [ exit for ]
next [ counter ]

参数：

for 循环示例：

该代码块将接受一个整数值作为其起始编号，然后使用 for 循环将该数字减小到零。它将打印每次迭代的结果。

sub reducetozero(numstart as integer)
dim i as integer
for i = numstart to 0 step -1
    debug.print "the number is now " & i
    if i = 0 then
        debug.print ("done!")
    end if
next i
end sub
sub testsub()
call reducetozero(10)
end sub

输出：

the number is now 10
the number is now 9
the number is now 8
the number is now 7
the number is now 6
the number is now 5
the number is now 4
the number is now 3
the number is now 2
the number is now 1
the number is now 0
done!

vba do until 循环

语法：

do until [condition]
    [statements]
    [exit do]
loop

参数：

do until 循环示例：

该代码块将接受一个整数值作为其起始编号，然后使用 do until 循环将数字增加到 10。它将打印每次迭代的结果。

sub incrementtoten(numstart as integer)
dim i as integer
i = numstart
do until i = 10   1
    debug.print "the number is now " & i
    i = i   1
loop
end sub
sub testsub()
call incrementtoten(-5)
end sub

testsub 输出：

the number is now -5
the number is now -4
the number is now -3
the number is now -2
the number is now -1
the number is now 0
the number is now 1
the number is now 2
the number is now 3
the number is now 4
the number is now 5
the number is now 6
the number is now 7
the number is now 8
the number is now 9
the number is now 10
done!

vba do while 循环

语法：

do while [condition]
    [statements]
    [exit do]
loop

参数：

do while 循环示例：

该代码块将接受一个整数值作为其起始编号，然后使用 do while 循环将该数字增加到 10。它将打印每次迭代的结果。

sub incrementtoten(numstart as integer)
dim i as integer
i = numstart
do while i < 10   1
debug.print "the number is now " & i
i = i   1
loop
debug.print "done!"
end sub
sub testsub()
call incrementtoten(-9)
end sub

testsub 输出：

the number is now -9
the number is now -8
the number is now -7
the number is now -6
the number is now -5
the number is now -4
the number is now -3
the number is now -2
the number is now -1
the number is now 0
the number is now 1
the number is now 2
the number is now 3
the number is now 4
the number is now 5
the number is now 6
the number is now 7
the number is now 8
the number is now 9
the number is now 10
done!

在 vba 中使用 exit 命令强制停止循环

在处理循环时，它们与循环在完成时将继续执行的条件绑定。然而，一个常见的场景是我们需要退出循环，即使条件仍然满足。一个典型的应用是在处理错误处理方法时，搜索时停止技术。需要立即退出循环以防止进一步的错误或节省执行时间。

下面的代码块将演示使用 exit 命令强制循环在 do 循环中停止。

此代码块旨在在两个数字的商为 1 时停止循环。这两个数字是在子程序的参数 upperbound 和 lowerbound 整数值之间随机生成的。如果生成的除数 (divis) 为零，则会发生错误，因为不允许除以零。为避免这种情况发生，我们将使用 exit 命令终止循环。

sub stopwhenquotientisone(upperbound as integer, lowerbound as integer)
dim divid as integer
dim divis as integer
dim isone as boolean
divid = int((upperbound - lowerbound   1) * rnd   lowerbound)
divis = int((upperbound - lowerbound   1) * rnd   lowerbound)
do until isone = true
    if divis = 0 then
        debug.print "illegal divisor. exiting the loop"
        exit do
    end if
debug.print divid / divis
if divid / divis = 1 then
    isone = true
    debug.print "done! one is achieved."
end if
divid = int((upperbound - lowerbound   1) * rnd   lowerbound)
divis = int((upperbound - lowerbound   1) * rnd   lowerbound)
loop
end sub
sub testsub()
call stopwhenquotientisone(4, -4)
end sub

testsub 输出（第一次试）：

-4 
-0 
-0.666666666666667 
illegal divisor. exiting the loop

testsub 输出（第四次试）：

-2 
 0 
-3 
 1 
done! one is achieved.

下面的代码块将演示使用 exit 命令强制循环在 for 循环中停止。

在这个例子中，stopwhennegative 子程序需要两个参数。首先是 startnum，然后是 endnum。循环将从 startnum 迭代到 endnum。如果计数器变为负数，则循环将由 exit 命令终止。

sub stopwhennegative(startnum as integer, endnum as integer)
dim i as integer
 
for i = startnum to endnum step -1
 
    if i < 0 then
        debug.print "opps, negative values detected. exiting loop."
        exit for
    end if
debug.print "the current number is :" & i
next i
end sub
sub testsub()
call stopwhennegative(10, -5)
end sub

testsub 输出：

the current number is :10
the current number is :9
the current number is :8
the current number is :7
the current number is :6
the current number is :5
the current number is :4
the current number is :3
the current number is :2
the current number is :1
the current number is :0
opps, negative values detected. exiting loop.