iOS 5 Programming Cookbook

1.7. Declaring Variables in Objective-C

Problem

You want to use variables with clear names in your iOS apps.

Solution

Apple conventions dictate certain rules for variable names. Determine the type of the variable (for instance, integer, array, string, etc.) and then a descriptive name for it. In an empty line of code, place the type of your variable first, following by its name. Variable names are advised to follow these rules:

1. Follow the camelCase naming convention. If the variable name is one word, all letters must be lowercase. If the variable name is more than one word, the first word must be entirely lowercase and the subsequent words must have their first letter uppercase and the rest of their letters lowercase. For instance, if you want to have a counter variable, you can simply name it counter. If you want to call your variable “first counter”, declare it firstCounter. The variable name “my very long variable name” would become myVeryLongVariableName. (Names of that length are quite common in iOS programs.)

2. Variables should ideally have no underline in their names. For instance, my_variable_name can and perhaps should be changed to myVariableName.

3. Variable names should contain only letters and numbers (no punctuation such as commas or dashes). This is a restriction in the Objective-C language and many other languages, but this helps keeping variable names tidy.

Let’s have a look at a few examples. There are a few primitive data types in Objective-C. A data type is a name that specifies ...