- 2.1 Representing Ordinary Strings
- 2.2 Representing Strings with Alternate Notations
- 2.3 Using Here-Documents
- 2.4 Finding the Length of a String
- 2.5 Processing a Line at a Time
- 2.6 Processing a Byte at a Time
- 2.7 Performing Specialized String Comparisons
- 2.8 Tokenizing a String
- 2.9 Formatting a String
- 2.10 Using Strings As IO Objects
- 2.11 Controlling Uppercase and Lowercase
- 2.12 Accessing and Assigning Substrings
- 2.13 Substituting in Strings
- 2.14 Searching a String
- 2.15 Converting Between Characters and ASCII Codes
- 2.16 Implicit and Explicit Conversion
- 2.17 Appending an Item Onto a String
- 2.18 Removing Trailing Newlines and Other Characters
- 2.19 Trimming Whitespace from a String
- 2.20 Repeating Strings
- 2.21 Embedding Expressions Within Strings
- 2.22 Delayed Interpolation of Strings
- 2.23 Parsing Comma-Separated Data
- 2.24 Converting Strings to Numbers (Decimal and Otherwise)
- 2.25 Encoding and Decoding rot13 Text
- 2.26 Encrypting Strings
- 2.27 Compressing Strings
- 2.28 Counting Characters in Strings
- 2.29 Reversing a String
- 2.30 Removing Duplicate Characters
- 2.31 Removing Specific Characters
- 2.32 Printing Special Characters
- 2.33 Generating Successive Strings
- 2.34 Calculating a 32-Bit CRC
- 2.35 Calculating the MD5 Hash of a String
- 2.36 Calculating the Levenshtein Distance Between Two Strings
- 2.37 Encoding and Decoding base64 Strings
- 2.38 Encoding and Decoding Strings (uuencode/uudecode)
- 2.39 Expanding and Compressing Tab Characters
- 2.40 Wrapping Lines of Text
- 2.41 Conclusion
This chapter is from the book
This chapter is from the book
This chapter is from the book
2.9 Formatting a String
This is done in Ruby as it is in C, with the sprintf method. It takes a string and a list of expressions as parameters and returns a string. The format string contains essentially the same set of specifiers available with C's sprintf (or printf).
name = "Bob"
age = 28
str = sprintf("Hi, %s... I see you're %d years old.", name, age)
You might ask why we would use this instead of simply interpolating values into a string using the #{expr} notation. The answer is that sprintf makes it possible to do extra formatting such as specifying a maximum width, specifying a maximum number of decimal places, adding or suppressing leading zeroes, left-justifying, right-justifying, and more.
str = sprintf("%-20s %3d", name, age)
The String class has a method % that does much the same thing. It takes a single value or an array of values of any type:
str = "%-20s %3d" % [name, age] # Same as previous example
We also have the methods ljust, rjust, and center; these take a length for the destination string and pad with spaces as needed:
str = "Moby-Dick" s1 = str.ljust(13) # "Moby-Dick" s2 = str.center(13) # " Moby-Dick " s3 = str.rjust(13) # " Moby-Dick"
If a second parameter is specified, it is used as the pad string (which may possibly be truncated as needed):
str = "Captain Ahab" s1 = str.ljust(20,"+") # "Captain Ahab++++++++" s2 = str.center(20,"-") # "——Captain Ahab——" s3 = str.rjust(20,"123") # "12312312Captain Ahab"