Strings in Visual Basic
Words, Phrases, and Spaces
Strings are a series of
characters.
ä
Constant strings never change and
are indicated by double quotes.
ä Examples:
“Fleeb”
“Here is a string.”
Strings are a series of
characters.
ä
Variable strings are a special type
of variable.
ä Example:
ä
Dim Fleeb as String
In any of the following operators
and functions you can use either a
variable or constant string.
Strings have their own
operators and functions.
Operators for putting strings together.
ä Functions for pulling strings apart.
ä Functions for creating strings.
ä Functions for modifying strings.
ä Operators for finding out things about
strings.
ä
Putting Strings Together
ä
& concatenates two strings
ä Examples:
“This “ & “is fun!” becomes “This is fun!”
ä “Fleeb” & “norb” & “ski” becomes
“Fleebnorbski”
ä
Old Operator
ä
The + sign can be used for the
same purpose, but it is better to use
the & since no one will mistake it
for addition.
Functions for Pulling Strings
Apart
ä
Left$ - Pulls off the leftmost characters.
ä Takes
two arguments,
the string
ä the number of characters to pull off
ä
ä Examples:
Left$(“Here is another string”,10) returns
“Here is an”
ä Left$(“6 + 67 * 9”,6) returns “6 + 67”
ä
Pulling Strings Apart
ä
Right$ - Pulls off the rightmost
characters.
ä Takes
two arguments:
the string
ä the number of characters to pull off
ä
ä Examples:
Right$(“Here is another string”,10)
returns “her string”
ä Right$(“6 + 67 * 9”,6) returns “67 * 9”
ä
Pulling Strings Apart
ä
Mid$ - Pulls out characters from middle.
ä Takes
three arguments
the string
ä the position to start pulling from.
ä the number of characters to pull.
ä
ä Examples:
Mid$(“Here is another string”,10,4) returns
“noth”
ä Mid$(“6 + 67 * 9”,5,2) returns “67”
ä
Creating Strings
Str$ - Creates a string from a
number.
ä CStr - Creates a string from a
number.
ä Format$ - Allows very complicated
formatting of numbers.
ä
Creating Strings
ä
Format$ - Used with numbers,
gives precise formatting control
over strings.
ä Takes
two arguments
A number
ä A descriptor.
ä
Descriptors for Format$
ä
Descriptors come in two flavors: system
defined and user defined.
System defined include: General Number,
Currency, Fixed, Standard, Percent,
Scientific, Yes/No, True/False, On/Off
ä User defined are generated using another
string. The other string has special characters
in it that define how the number should be
displayed.
ä
User Defined Format String
Characters
0
#
.
%
,
E
:
/
\ ”
Display a number or zero.
Display a number or nothing.
Decimal placeholder
Percentage placeholder.
Thousands seperator
Scientific Notation
Time seperator
Date seperator
Literal character indicator.
User Defined Format String
Characters
ä
ä
ä
ä
ä
ä
ä
ä
d
m
y
h
n
s
w
q
Day
Month
Year
Hour
Minute
Second
Day of Week
Quarter
Some Examples of Format
format(10201.2,”000000.00”) ->
010201.20
ä format(11.1,”####.##”) -> 11.1
ä format(10010021,”###,###,###”) ->
10,010,021
ä format(1000000,”#.##E##”) ->
1.00E6
ä
Some Examples of Format
Using Time Formats
Dim curr_time as double
curr_time = Now
format(cur_time,”mm/dd/yy hh:nn”) ->
03/06/95 09:15
format(cur_time,”m/d/yy h:n”) ->
3/6/95 9:15
More Examples
format(cur_time,”dddd, mmm dd, yyyy”)
Wednesday, Dec. 06, 1995
Functions for Modifying
Strings
UCase$ - Make every letter upper
case.
ä LCase$ - Make every letter lower
case.
ä Trim$ - Removes leading and
trailing spaces from the string.
ä
Modifying Strings
ä
UCase$ - Make every letter upper
case.
ä Takes
one argument, the string.
ä Examples
UCase$(“Here”) returns “HERE”
ä UCase$(“Oh Boy”) returns “OH BOY”
ä
Modifying Strings
ä
LCase$ - Makes every letter lower
case.
ä Takes
one argument, the string.
ä Examples
LCase$(“Here”) returns “here”
ä LCase$(“Oh Boy”) returns “oh boy”
ä
Modifying Strings
ä
Trim$ - Removes leading and trailing
spaces from string
ä Takes
one argument, the string
ä Examples Trim$(“
Here is a string
returns “Here is a string”
ä
“)
Also comes in LTrim$ and RTrim$, for
removing only one end or the other.
Functions for Finding Things
Out About Strings
Len - Finds out how long the string is.
ä InStr - Finding out if one string is in
another.
ä StrComp - Find out which string is
“bigger”.
ä
Finding Out about Strings
ä
Len - Finds out how long the string is.
ä Takes
ä
ä
one argument
A string
Returns the number of characters in
the string.
Finding Out about Strings
ä
InStr - Finding out if one string is in
another.
ä Takes
two arguments
The string to look in.
ä The string to look for.
ä
ä Returns
the location of the first occurance
of string two in string one.
ä If the location equals zero, there is no
occurrence of string one in string two.
Finding Out about Strings
ä
StrComp - Which string is “bigger”.
ä Takes
two arguments:
string one
ä string two
ä
ä Returns:
-1 if string one < string two
ä 0 if they are equal
ä 1 if string two < string one
ä
Summary
String operations can be very
useful.
ä VB gives particularly strong
support for strings.
ä