Rails WHERE method in the context of SCOPE for like ? syntax

I fail to find the right syntax for a WHERE method in the context of a SCOPE. My classified MODEL has several SCOPE that works well to filter classifieds by category or area:

#in the model  
scope :filter_by_category, -> (category) {where category: category}
scope :filter_by_area, -> (area) {where area: area}

I want to do a more advanced SCOPE filter to search for classifieds' Titles containing a specific string. Outside of SCOPE I would generally retrieve the data with:

Classified.where("title like ?", "%title%")

But in the context a SCOPE, I do not manage to find the right syntax and keep getting some errors (unexpected ->, expecting `end' scope [...]). I tried the following:

scope :filter_by_title -> (title) { where ("title like ?","%title%")}
scope :filter_by_title -> (title) { where ("like ?","%title%")}

Both give me syntax error. Could anyone help me find the right syntax please?

Solution

You have three problems:

The lambda is an argument to scope to you need a comma after the symbol:
```
 scope :filter_by_title, -> ...
 # --------------------^
```
Whitespace matters in Ruby so f (x, y) and f(x, y) are different things. The parentheses in f (x, y) are expression grouping parentheses whereas in f(x, y) they're method calling parentheses. So f (x, y) is a syntax error because x, y isn't an expression. Remove the stray space:
```
scope :filter_by_title, ->(title) { where('title like ?', ...
# ---------------------------------------^ No more space here
```

You want to use string interpolation to expand the title argument to the scope:

scope :filter_by_title, ->(title) { where('title like ?', "%#{title}%") }
# ----------------------------------------------------------^^-----^ Interpolation