When you use named arguments in a function call, you can freely change the order they are listed in, and if you want to use their default values, you can just leave these arguments out altogether. Consider the following function, reformat , which has 4 arguments with default values. You are also able to skip specific arguments with default values, rather than omitting them all.
However, after the first skipped argument, you must name all subsequent arguments:. You can pass a variable number of arguments vararg with names using the spread operator:. If a function does not return a useful value, its return type is Unit.
Unit is a type with only one value - Unit. This value does not have to be returned explicitly:. The Unit return type declaration is also optional. The above code is equivalent to:. Explicitly declaring the return type is optional when this can be inferred by the compiler:. Functions with block body must always specify return types explicitly, unless it's intended for them to return Unit , in which case specifying the return type is optional. Kotlin does not infer return types for functions with block bodies because such functions may have complex control flow in the body, and the return type will be non-obvious to the reader and sometimes even for the compiler.
I prefer object literal definitions even in C for managing complex methods because you can explicitly see which properties are being set when an object is instantiated. You'll have to do a little more work to handle default arguments but in the long run your code will be a lot more readable. With object literal definitions you can break your dependence on documentation to understand what your code is doing at first glance.
Note: If I remember right readonly access control should work for object literal constructors in C. They essentially work the same as setting properties in the constructor. It can be an enlightening experience. I probably should have provided examples to demonstrate use in a statically typed language but I'm not currently thinking in a statically typed context.
Basically, I've been doing too much work in a dynamically typed context to suddenly switch back. What I do know is object literal definition syntax is completely possible in statically typed languages at least in C and Java because I have used them before.
In statically typed languages they're called 'Object Initializers'. Here are some links to show their use in Java and C. Very much like Evan Plaice is saying, I'm a huge fan of simply passing associative arrays or your language's comparable data structure into functions whenever possible. Wordpress does a lot of stuff this way, and I think it works well. Though my example code above is imaginary, and is not itself an example from Wordpress.
This technique allows you to pass a lot of data into your functions easily, yet frees you from having to remember the order in which each must be passed.
You'll also appreciate this technique when comes time to refactor - instead of having to potentially change the order of a function's arguments such as when you realize you need to pass Yet Another Argument , you don't need to change your functions's parameter list at all. Not only does this spare you from having to re-write your function definition - it spares you from having to change the order of arguments each time the function is invoked.
That's a huge win. A previous answer mentioned a reliable author who stated that the less parameters your functions have, the better you are doing. The answer did not explain why but the books explains it, and here are two of the most convincing reasons as why you need to adopt this philosophy and with which I personally agree with:.
Parameters belong to a level of abstraction which is different from that of the function. This means the reader of your code will have to think about the nature and the purpose of the parameters of your functions: this thinking is "lower level" than that of the name and the purpose of their corresponding functions.
The second reason to have as less parameters as possible to a function is testing: for example, if you have a function with 10 parameters, think about how many combinations of parameters you have to cover all the test cases for, for instance, a unit test. To provide some more context around the advice for the ideal number of function arguments being zero in Robert Martin's "Clean Code: A Handbook of Agile Software Craftsmanship", the author says the following as one of his points:.
Arguments are hard. They take a lot of conceptual power. That's why I got rid of almost all of them from the example. Consider, for instance, the StringBuffer in the example.
We could have passed it around as an argument rather than making it an instance variable, but then our readers would have had to interpret it each time they saw it. The argument is at a different level of abstraction that the function name and forces you to know a detail in other words, StringBuffer that isn't particularly important at that point. For his includeSetupPage example above, here's a small snippet of his refactored "clean code" at the end of the chapter:.
The author's "school of thought" argues for small classes, low ideally 0 number of function arguments, and very small functions. While I also don't fully agree with him, I found it thought-provoking and I feel that the idea of zero function arguments as an ideal can be worth considering. Also, note that even his small code snippet above has non-zero argument functions as well, so I think it depends on the context. And as others have pointed out, he also argues that more arguments make it harder from a testing point of view.
But here I mainly wanted to highlight the above example and his rationale for zero function arguments. Ideally zero. One or two are ok, three in certain cases. Four or more is usually a bad practice. As well as the single responibility principles that others have noted you can also think of it from testing and debugging perspectives.
If there is one parameter, knowing it's values, testing them and finding error with them is 'relatively easy as there is only one factor. As you increase the factors, the total complexity increases rapidly. For an abstract example:. Consider a 'what to wear in this weather' program. Consider what it could do with one input - temperature.
As you can imagine, the results of what to wear are pretty simple based on that one factor. Now imagine how hard it would to debug if it gave the 'wrong' answer to something.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Are there guidelines on how many parameters a function should accept? Ask Question. Asked 9 years, 7 months ago. Active 2 years, 9 months ago. Viewed k times. Among the above five variables, the first two belong to the variables passed in during the call.
This article will also focus on their characteristics. A parameter is a variable passed in by the main calling function. Compared with other programming languages, JS has less restrictions on passing parameters. Any value can be used as a parameter. Just because of this, there are many unfamiliar places when you first contact or transfer from other languages. Here are some common problems:. This is a very basic problem. Here is an example:. Reference data type parameters, such as objects, are also passed into methods by value.
This means that when the method returns, the passed-in reference still references the same object as before. However , the values of the object's fields can be changed in the method, if they have the proper access level. Inside the method, circle initially refers to myCircle. The method changes the x and y coordinates of the object that circle references that is, myCircle by 23 and 56, respectively. These changes will persist when the method returns.
This reassignment has no permanence, however, because the reference was passed in by value and cannot change. Within the method, the object pointed to by circle has changed, but, when the method returns, myCircle still references the same Circle object as before the method was called.
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