Stringer
fmt.Stringer is a Go standard-library interface implemented by a type with a parameterless String method returning a textual representation.
Learn Go with Pocket-Sized Projects
The Stringer interface is the fmt convention satisfied by a type with a parameterless String method returning a string.
- How it is used
- Formats domain values through Go’s fmt printing and formatting functions.
- How deep it goes
- Defines the one-method contract and demonstrates implementations, formatting behavior, composition, and receiver choices.
- Examples
- Demonstrates hint, feedback, Currency, Decimal, and Amount values with custom textual representations.
- What you can do after
- Apply it via fmt.Print* and formatting verbs to produce readable representations for custom Go types.
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Go in Action, Second Edition
Stringer is a Go interface conventionally satisfied by a type that provides a String method for custom textual formatting.
- How it is used
- Uses Stringer to control how domain values appear when formatted by fmt.Printf and similar functions.
- How deep it goes
- Explains the method contract, naming convention, structural satisfaction, and compile-time verification.
- Examples
- Formats measurement units using common abbreviations and an underlying-string fallback.
- What you can do after
- Apply it by implementing String() so Go formatting functions display domain values meaningfully.
Go in Practice, Second Edition
fmt.Stringer is a Go standard-library interface implemented by types that provide a parameterless String method returning a string.
- How it is used
- Uses Stringer to recognize values that provide their own string representation and to demonstrate interface conformance checks.
- How deep it goes
- Defines the method shape and demonstrates assertion and reflection checks, without developing broader formatting behavior.
- Examples
- Demonstrates Stringer with a Name type and compares it against io.Writer using runnable assertion and reflection examples.
- What you can do after
- Apply type assertions or the reflect package to determine whether values or types implement Stringer.
Related concepts
- natural language interfacekind of · A natural language interface enables interaction with a system through human-language text or speech.
- currencyimplemented by · Currency is a system and unit of money used to express monetary value, facilitate exchange, and denominate financial amounts.
- monetary amountimplemented by · A monetary amount is a quantity of money represented by a numeric value together with a currency.
- interfacekind of · A software interface is a contract or boundary that specifies the operations, properties, or capabilities through which types or components interact, without requiring a particular implementation.
- string formattingused by · String formatting is the construction of text from values according to a specified format or template.
- fmtuses · fmt is a software library or package that provides formatted text generation and, in some implementations, formatted input and output operations.
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