VBScript - Working With Strings

Basics

Special characters

Getting the string length

Concatenating strings

Comparing strings

Accessing individual character of a string

Searching for characters and substrings

Getting a substring

Splitting strings

Removing extra spaces from a string

Replacing characters and substrings

Changing the letter case

Working with string lists

A String is a sequence of symbols or digits. Strings are among the most frequently used data types. Like any other data type, strings in TestComplete are represented as OLE-compatible variants. In VBScript, a sequence of literal characters, enclosed in double quotes ("), is recognized as a string. Single quotation marks (') are allowed within a string. To insert a double quotation mark into a string, it should be duplicated. The following is an example of string:

To deal with strings, TestComplete has a special aqString scripting object. The object is available for all supported scripting languages, so that you can use it to operate with string values regardless of the chosen language.

Another scripting object that is useful for string manipulation is aqConvert. This object has several methods that convert values of different types to a string representation and vice versa.

Furthermore, you can use native VBScript functions that operate with strings. A detailed description of VBScript functions can be found in the Functions (VBScript) article of the MSDN library. The table below only lists major functions:

In VBScript you can emulate any character by using the Chr function with the appropriate ASCII code. This also applies to special characters that are used to format string values. Alternatively, you can emulate control characters using native string constants. The table below lists the most frequently used special characters and their constants.

Special characters obtained by a function or constant should be joined to the string by concatenation:

To obtain the total number of characters in a string, you can call either the aqString.GetLength method, or the Len function of VBScript. The character position in VBScript is not zero-based, so the maximum position number in a string equals the string length. The following code demonstrates both ways of obtaining the string length:

Using TestComplete, you can limit the length of string parameters returned by functions of the tested application. For this purpose, use the Maximum string length of [out] parameters project property. If the length of the string returned from the application via one of its out parameters exceeds the property’s value, TestComplete treats the returned string as a null one.

The operation that forms a string out of several others is called concatenation. The aqString object has special method aqString.Concat that perform this operation. In VBScript the concatenation is performed both by plus (+) and by ampersand (&) operators. The plus operator is intended to perform addition, but if both operators are strings, then string concatenation occurs. However it is more convenient to use the ampersand operator since it does not require a preliminary conversion to a string type.

This sample code shows how to make a string out of several substrings:

String comparison is widely used during testing. Generally, a test procedure obtains textual data (user input, file contents, property values and so on) and then compares it with the expected data. That is why both TestComplete and VBScript have their own methods to compare one string value with another. These methods are: aqString.Compare and StrComp.

The aqString.Compare method has three parameters: two of them, String 1 and String2, specify the strings to be compared; the third parameter (CaseSensitive) defines whether the comparison should be case-sensitive or not.

Similarly, VBScript's StrComp function has two mandatory parameters, Str1 and Str2, that define the compared strings, and one optional parameter, CompType, that specifies the comparison type. The CompType parameter can accept the following values: vbBinaryCompare (or 0), and vbTextCompare (or 1). vbBinaryCompare means binary case-sensitive comparison. vbTextCompare means case-insensitive comparison. The default type is vbBinaryCompare. The function result is -1 if Str1 is less than Str2, 1 if Str1 is greater than Str2 and they equal 0 if the strings are the same.

Both methods can compare strings holding specific national symbols, for example characters with diacritical marks ( , , and others).

The code below demonstrates how to use both methods:

The VBScript scripting language has no data type that can be used to store single symbols. However, this is not a problem, since the string type can hold both a series of characters and individual characters. Moreover, you can extract a single character from a string using the aqString.GetChar method and VBScript’s Mid function. The latter retrieves the given number of characters starting from the specified position. Note however that the VBScript function uses 1-based indexes, whereas the GetChar method uses zero-based indexes. The sample routine below demonstrates how to use both of these routines. It posts text to TestComplete log in two different ways: as a whole string and by a single letter.

One of the most common tasks that one has to perform when working with string values is determining whether specific text is part of a string. To perform such tasks, the aqString object has the Find method. If the specified substring was found, the method returns the number of the first occurrence of the substring within the source string. If the specified substring was not found, the method returns -1:

You can also get the position where the specified substring occurs using the VBScript functions InStr and InStrRev. They both return the initial position (from 1) of the first substring match, but the first one searches from left to right, while the other from right to left. If the substring was found, the functions return the initial position of the first substring match. If no occurrences were found, they return 0. The code below demonstrates how to use the InStr function:

VBScript has several methods that allow you to extract a substring out of a string. They are Left, Right and Mid. These methods vary in how the extracted substring is defined.

Function Left returns a text fragment that starts at the beginning of the given string and has the specified length. Function Right does a similar action, but it gets the last fragment of the given string. If the fragment’s length is greater than the length of the whole string, then the entire string is returned. Negative length values are not allowed, zero-length returns an empty string.

Function Mid returns a text fragment that starts at a given position and has a specified length. The length parameter is optional, and if it is omitted then the resulting substring continues up to the end of the source string.

The aqString object also has a similar method, SubString that returns a substring that starts from the specified position and has the given length. However, this method requires all tree parameters, and position numbers are zero-based.

The sample code below demonstrates how to use these functions:

Sometimes it is required to make several strings out of a single string. This operation splits a string into substrings. It can be performed by VBScript's native function called Split. This routine searches the string for a delimiter character, separates the string and returns an array holding the constituent strings. If the delimiter is omitted, then the space character is assumed as a delimiter. Also you can constrain the maximum array length with the third parameter and set the comparison method with the forth. They are not obligatory and can be omitted. The same method can be used to split a string onto substrings, sentences and even separate words; it all depends on the specified delimiter. The first sample routine below uses a space character as a delimiter to extract words out of a string, and the second routine splits the string by line breaks:

TestComplete has a similar method called aqString.GetListItem. It extracts a substring with the specified index from the input string. It was designed to read items from a string list, see Working with string lists for more information. However, it allows you to redefine the delimiter characters and, like the Split method, it can be used to get sentences, single words and so on.

The aqString object has a special routine, aqString.Trim, that excludes leading and trailing spaces (or both) from a string. VBScript has also the LTrim, RTrim and Trim functions that exclude, leading, trailing and both leading and trailing spaces from the input string. Generally, all these methods are used to remove unnecessary spaces at the beginning or at the end of strings obtained from the user input.

Another function that can be useful when handling user input strings is excluding extra inner spaces out of the string. This function seems to be similar to Trim, but the latter only removes spaces at the beginning or end of the string and does not affect the spaces inside the string. The general idea of the function is for the string to be parsed into separate words and then a new string is constructed. The new string consists of the same words but is separated with a single space between words.

Quite often we need to find and replace a character or substring within a string. There are two ways to do this: by using the aqString.Replace method or by using the Replace method of a RegExp object.

The aqString object method is much easier to use. It can be used when you need to change a certain character or string. It allows you to set whether the search should be case-sensitive or not. Here is an example of how to use this method:

The RegExp.Replace method is a little more complicated, but it offers more flexibility. You can not only change a definite character or string, but all fragments matching the specified regular expression pattern. However you have to create an instance of the RegExp object and set the pattern before replacing. The regular expression pattern is enclosed in double quotation marks ("). Additionally you can specify the following Boolean flags that affect the search procedure: RegExp.Global - performs a global search for all occurrences of a pattern, RegExp.IgnoreCase - searches regardless of the letter case and RegExp.MultiLine - performs a multi-line search. For a full description of how to use regular expressions, refer to the Introduction to Regular Expressions article in the MSDN library.

The first sample demonstrates how to change a definite string using the replace method.

The second example shows how to replace a substring with alternative parts. The patterns of alternative parts are separated by pipe characters (" | "). For instance in the sample below the "ht(ml|m)" pattern matches both html and htm:

Furthermore, using regular expressions you can search for the text fragments that match the specified format. In the next sample, all dates written in the DD/MM/YYYY format are substituted with the Some Date string. This operation can be useful, for example, when comparing two reports that contain the generation date.

A string can contain both uppercase and lowercase letters. The TestComplete aqString object and the native String object have methods that convert uppercase letters to lowercase and vice versa. They are: aqString.ToLower, aqString.ToUpper, LCase and UCase.

The code below demonstrates how all of these methods are applied.

Some scripting objects, generally, controls like ListBoxes, ComboBoxes and Memos, return information about their state or contents as string lists. Individual data elements (or items) in this list are separated by commas, line breaks, carriage returns or some other delimiter characters.

The aqString object has a number of specific methods (AddListItem, ChangeListItem, DeleteListItem, GetListItem and GetListLength) that are used to work with such lists. AddListItem and DeleteListItem add an item to or remove if from the list respectively. The GetListItem method retrieves the item with the given index, and ChangeListItem assigns a new value to the given item. The GetListLength method returns the total number of items in the string list.

The symbol that is used as the separator between list items is defined by the ListSeparator property. By default, the list separator is a pipe (|), but it can also be a comma, column, line break, carriage return, tabulation, and any other printable and non-printable character, or even several characters.

Here is sample code that demonstrates how to work with the string lists returned by scripting objects.