I have specific flattened property names that I need to validate. Basically, what's valid is alpha-numeric string that can be followed by an array index ([4] for example), but doesn't have to be. If it's followed by a next word, then it has to be joined by a dot.
To illustrate, some of the examples that would be valid are:
parent[0].child
parent.child
parent.child1.list[0].child2
parent[500].child
parent0.child
par50ent.child
parent[0].child1[20].child[0]
And some invalid examples are
parent..child
parent[].child
parent[1a].child
parent[a].child
.parent
parent.
I don't know much about regular expressions, so what I came up with is this following line:
(([a-zA-Z0-9]{1,})(\[[0-9]{1,}\]){0,1}){1}((\.){1}([a-zA-Z0-9]{1,})(\[[0-9]{1,}\]){0,1}){0,}
While this does work, it's just too verbose. There has to be a nicer, shorter way to write this.
CodePudding user response：
You may use this regex to match only valid cases:
^\w (?:\[\d ])?(?:\.\w (?:\[\d ])?)*$
RegEx Details:
^: Start\w: Match 1 word characters(?:\[\d ])?: Match optional[<digits>]part(?:: Start a non-capture group\.: Match a dot\w (?:\[\d ])?: Match a word followed by optional[<digits>]
)*: End non-capture group. Repeat this group 0 or more times$: End
You may use this regex if you want to allow parent[0][1].child as well:
^\w (?:\[\d ])*(?:\.\w (?:\[\d ])*)*$
CodePudding user response：
Assuming that letters are English ones (A..Z or a..z) while digits are 0..9, you can try
^[A-Za-z] [A-Za-z0-9]*(?:\[[0-9] \])*(?>\.[A-Za-z] [A-Za-z0-9]*(?:\[[0-9] \])*)*$
pattern:
^ - anchor, string start
[A-Za-z] - starts from letter
[A-Za-z0-9] * - can contain zero or more letters or digits
(?:\[[0-9] \])* - can end by zero or more [digits] indexers
(?>\. ...)* - followed by zero or mo costructions each of them
starts from dot . and has syntax equals to the one above
$ - anchor, string end
Edit: please, note atomic group (?> ...) to prevent catastrophic bactracking (see The fourth bird's comment below)