Ive found the following places which well have a violation of the law of demeter. The law of demeter doesnt mean one dot yegor bugayenko. Violations of the law of demeter inside of the bll. Law of demeter and how to work with it programming ideas with.
The law of demeter is not a dot counting exercise youve. Difference between singleton and static class in java. Anything we use as a signal of a potential problem needs to have a low falsepositive rate. Yes, a bunch of getters for presentation code would likely be a violation of lod. The law of demeter states that you can access anything inside the object you are in, the method parameters you got, or any object created during the call. One comment on law of demeter and how to work with it. Exposing internal arrays to the caller violates object. This paper describes a software framework for identifying the law of demeter violations in programs sourcecode. It seems like simple getters are easiest here, but would potentially violate lod. I recommend completely disregarding the law of demeter. Method of object, which is held in instance variable 4.
A fluent api does not necessarily violate the law of demeter, since not all chain calls violate the law of demeter. The guideline was proposed by ian holland at northeastern university towards the end of 1987, and can be succinctly summarized in each of the following ways. Principle of least knowledge or law of demeter lod. In short, the intent of this law is to prevent you from reaching into an object to gain access to a third objects methods. In most cases, things which are easier for humans are easier for machines. We could try to regard it as a suggestion, instead of a law, but that isnt a good idea either. Answering otavioi think, the law of demeter speaks of specifying the contextstate explicitly and thus reduce the burden of learning. The law of demeter or principle of least knowledge is a design guideline for developing software, particularly objectoriented programs. Static property access warning must not be flagged for law of. For classes that only have static methods, consider making them utility classes. According to law of demeter, a method m of object o should only call following types of methods.
Law of demeter also known as principle of least knowledge is a. However, when it comes to factories or even design patterns like state pattern, we violate this analogy. It discusses the main challenges related to language constructs and static code. In its general form, the lod is a specific case of loose coupling.
The law of demeter lod or principle of least knowledge is a design guideline for developing. The law of demeter for functions or methods, in java attempts to minimize coupling between classes in any program. Principle of least knowledge or law of demeter lod may 19, 2011 leave a comment the principle states. Calling code has to know what type of thing it is trying to select and match to the appropriate property. See how the law of demeter stacks up with getters, chain calls, and other. The paperboy does not have direct access to the wallet. At the method level, the lod leads to narrow interfaces, giving access to only as. The problem with accessing static variables is that you are enforcing an external state to the class that is hard to test. Breaking the law of demeter is like looking for a needle.
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