Documentation
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Overview ¶
Package csvx provides convenience wrappers around encoding/csv.
It provides a set of Decode functions, that populate struct fields with delimiter-separated values.
Decode Accepted Types ¶
The T type parameter for Decode functions accepts structs. Fields may be of types bool, int*, uint*, float* or string for automatic parsing. For manual parsing with a method, any type is allowed. Unexported fields are ignored.
Decode Default Behavior ¶
DecodeFile and DecodeReader match column to field according to their order. For example:
type a struct {
Name string // Matches first column
Age int // Matches second column
Height float64 // Matches third column
}
DecodeFileHeader and DecodeReaderHeader match column to field according to the first line and the field's name, case insensitively. For example:
type a struct {
Name string // Matches a column titled name, Name, nAmE, etc.
Age int // Matches a column titled age, Age, aGe, etc.
Height float64 // Matches a column titled height, Height, hEiGhT, etc.
}
Note that the Header functions use the first line as metadata, while the other two functions expect data starting from the first line. In all functions yielding continues upon parsing errors, so that a caller may choose to skip lines.
Decode Field Tags ¶
Field tags can be used to change the default behavior. The format for a field tag is as follows:
Field int `csvx:"column,modifier1,modifier2..."`
The column part may be:
- empty: use the default behavior
- column name or index: associate this field with the column with this name or at this 0-based index, case sensitively
- "-": a single hyphen, ignore this field entirely
Modifiers may be:
- "allowempty": the input value may be empty, in which case no parsing will be attempted
- "optional": don't err if the column for this field is missing
- exported method name: use T's method with this name to parse the input value
A custom parsing method will replace the default parsing. The method's signature must take a string as input, and return the field's type and an error.
Index ¶
- func DecodeFile[T any](file string, mods ...ReaderModifier) iter.Seq2[T, error]
- func DecodeFileHeader[T any](file string, mods ...ReaderModifier) iter.Seq2[T, error]
- func DecodeReader[T any](r io.Reader, mods ...ReaderModifier) iter.Seq2[T, error]
- func DecodeReaderHeader[T any](r io.Reader, mods ...ReaderModifier) iter.Seq2[T, error]
- func File(file string, mods ...ReaderModifier) iter.Seq2[[]string, error]
- func Reader(r io.Reader, mods ...ReaderModifier) iter.Seq2[[]string, error]
- func TSV(r *csv.Reader)
- type ReaderModifier
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func DecodeFile ¶
DecodeFile returns an iterator over parsed instances of T, using column numbers for matching columns to fields.
fn is an optional function for modifying the CSV parser, for example for changing the delimiter.
func DecodeFileHeader ¶
DecodeFileHeader returns an iterator over parsed instances of T, using the first line for matching columns to fields.
fn is an optional function for modifying the CSV parser, for example for changing the delimiter.
func DecodeReader ¶
DecodeReader returns an iterator over parsed instances of T, using column numbers for matching columns to fields.
fn is an optional function for modifying the CSV parser, for example for changing the delimiter.
Example ¶
type person struct {
Name string
Age int
}
input := strings.NewReader("alice,30\nbob,25")
for p, err := range DecodeReader[person](input) {
if err != nil {
panic(err)
}
fmt.Println(p.Name, "is", p.Age, "years old")
}
Output: alice is 30 years old bob is 25 years old
func DecodeReaderHeader ¶
DecodeReaderHeader returns an iterator over parsed instances of T, using the first line for matching columns to fields.
fn is an optional function for modifying the CSV parser, for example for changing the delimiter.
Example ¶
type person struct {
Name string
Age int
}
input := strings.NewReader(
"user_id,age,city,name\n" +
"111,30,paris,alice\n" +
"222,25,london,bob")
for p, err := range DecodeReaderHeader[person](input) {
if err != nil {
panic(err)
}
fmt.Println(p.Name, "is", p.Age, "years old")
}
Output: alice is 30 years old bob is 25 years old
func File ¶
File iterates over CSV entries from a file. Applies the given modifiers before iteration.
Types ¶
type ReaderModifier ¶
ReaderModifier modifies the settings of a CSV reader before iteration starts.
Source Files