Core · Module 5 · Lesson 1 of 6
Classes and Access Control: Building Your First Type
Turn a struct into a class that guards its own invariants, with private data, public operations and a constructor that leaves every object valid.
By the end you can
- Explain what private buys over a plain struct
- Write a constructor that establishes the class invariant
- Predict the lifetime of a stack object and when its destructor runs
Builds on Binary Files: Writing and Reading Raw Bytes.
01 · A question first
Your contact-book struct lets anyone set the age to -400. The compiler does not complain, the file still writes, and the bug surfaces three weeks later in a report. What if the type itself refused to hold a bad value, so no function could ever see one?
Make a guess before you read on.
02 · The idea
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What's inside
- Start with the problem
- How the idea works
- Why it is correct
- What it costs
- Pitfalls and variations
- Where it is used
03 · Practice
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