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instance method

StringScanner#[]

(::Integer) -> ::String?

[](specifier) → substring or nil

static VALUE
strscan_aref(VALUE self, VALUE idx)
{
    struct strscanner *p;
    rb_len_t i;

    GET_SCANNER(self, p);
    i = resolve_capture_index(p, idx);
    if (i < 0) return Qnil;

    return extract_range(p,
                         adjust_register_position(p, p->regs.beg[i]),
                         adjust_register_position(p, p->regs.end[i]));
}

Returns a captured substring or nil; see Captured Match Values.

When there are captures:

Example

scanner = StringScanner.new('Fri Dec 12 1975 14:39')
scanner.scan(/(?<wday>\w+) (?<month>\w+) (?<day>\d+) /)

specifier zero: returns the entire matched substring:

Example

scanner[0]         # => "Fri Dec 12 "
scanner.pre_match  # => ""
scanner.post_match # => "1975 14:39"

specifier positive integer. returns the nth capture, or nil if out of range:

Example
```
scanner[1] # => "Fri"
scanner[2] # => "Dec"
scanner[3] # => "12"
scanner[4] # => nil
```
specifier negative integer. counts backward from the last subgroup:

Example
```
scanner[-1] # => "12"
scanner[-4] # => "Fri Dec 12 "
scanner[-5] # => nil
```

specifier symbol or string. returns the named subgroup, or nil if no such:

Example

scanner[:wday]  # => "Fri"
scanner['wday'] # => "Fri"
scanner[:month] # => "Dec"
scanner[:day]   # => "12"
scanner[:nope]  # => nil

When there are no captures, only [0] returns non-nil:

Example

scanner = StringScanner.new('foobarbaz')
scanner.exist?(/bar/)
scanner[0] # => "bar"
scanner[1] # => nil

For a failed match, even [0] returns nil:

Example

scanner.scan(/nope/) # => nil
scanner[0]           # => nil
scanner[1]           # => nil

See also #<< #beginning_of_line? .new #captures also in 4.0 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

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