Summary: Functions
Updated for Xcode 13.3
We’ve covered a lot about functions in the previous chapters, so let’s recap:
- Functions let us reuse code easily by carving off chunks of code and giving it a name.
- All functions start with the word
func, followed by the function’s name. The function’s body is contained inside opening and closing braces. - We can add parameters to make our functions more flexible – list them out one by one separated by commas: the name of the parameter, then a colon, then the type of the parameter.
- You can control how those parameter names are used externally, either by using a custom external parameter name or by using an underscore to disable the external name for that parameter.
- If you think there are certain parameter values you’ll use repeatedly, you can make them have a default value so your function takes less code to write and does the smart thing by default.
- Functions can return a value if you want, but if you want to return multiple pieces of data from a function you should use a tuple. These hold several named elements, but it’s limited in a way a dictionary is not – you list each element specifically, along with its type.
- Functions can throw errors: you create an enum defining the errors you want to happen, throw those errors inside the function as needed, then use
do,try, andcatchto handle them at the call site.
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