I know when building an Angular app (or other frontend framework with auto UI update by change detection), using function in a template is not recommended since it will result in the function being called every time when change detection runs. This means if we want to display a value derived from another value, we have to explicitly create another field to store that derived value. For example, if I want to display a temperature in both C and F and my model only stores the value of C, I have to compute the value of F from C, then store in a separate field, and display both fields in the template. Dose this considered breaking Single Source Of Truth? Are we essentially trading for performance, in the cost of having code smell?

1 Answer 1


Yes, thats how it is.

Software Development is the Art of Trade-Offs.

You could display the content of variables, and update those by hooking into the life cycle of the framework and there do a check if an update is necessary and then call your update methods.
If your method is a pure function you could easily implement a memorisation (store input/output combinations and reuse them instead of recalculating the values each time).

But its a trade-off.
You can choose between a not optimal performance, a code smell or complicated code.

Therefore it totally depends on the context which one is the "best" solution.

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