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The state button issues, whenever you want to change the state of your object, but you don't want

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to have these changes in the underlying class.

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It is a very good choice for factoring in classes where you use many, if else, statements.

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Imagine having a product in a store, the product can take multiple states, the product can be for

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sale or it can be sold or even borrowed.

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With this backing, you delegate the state changes to the respective state objects.

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So you won't need to rely on many, if any, statements to capture the changes in the state of the initial

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object.

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Looking at the U.N. diagram, the context object would be the product.

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The state interface will contain the contract for the state implementation.

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The context clause will delegate its state to the concrete state implementations.

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You can have many implementations, not just you, but for simplicity.

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The standard diagram for this matter includes only two.

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Let's see how this pattern can be implemented.

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Endako.