I like the idea of a total ban of carrying with authorized exceptions for certain practitioners (similar to guns here in Europe), but I feel also it'd very hard to implement. A switchblade knife can be used to kill and it's very easily concealed in a small pocket. Nobody sees it until it's too late - actually a super-important warning sign if you feel someone has ill intent is to look if they have their hands visible or in pockets. In the latter case - it's imperative they don't get close. And once a guy carrying is found, it's usually because he's already used the blade
And for what matters, my kitchen chef knives are just as deadly.
Random checks feel like a medicine worse than the sickness - there's already so much rise in the power of police and government over the common person due to technology advances.
On the other hand, going around with a tachi- or katana-sized sharp blade is quite evident... but nobody probably reports it because everybody mind their business, which is in general a good thing.
So it's a conundrum.
Unfortunately, the most obvious option is the one I don't like much at all: targeted checks on specific segments of population who have a higher probability to carry blades for actual violent use.
Here in Oslo, Norway for example there's a steep increase in very young boys in gangs (from 12-13 yo up) carrying blades, and using them to intimidate and steal from other boys of the same age. Some months ago a 14yo actually killed a man stabbing him because he felt threatened, and he's now been released: the police can't do much because here minors aren't under it jurisdiction. It's an increasingly bad situation and people begins to feel insecure in letting their children go around alone in town.
It's a very touchy subject given the nature of the issue, and politicians of course don't help as they either use the problem to gain popularity with populistic means, appealing to race and background and hinting to the fools who judge people by looks that's it's an "immigration" or "asylum seekers" problem (like there weren't local criminals); and others ignore the problem altogether in the name of well-meant antiracism and aspiration to equality.
In short, I have no clue what's the best thing to do. A ban would however decrease the likelihood of incidents a bit, not to zero, but lower it - so I tend to be in favor.