Swift closure capture or not

capture.swift

var a = 1
var b = 1

//Do not capture
let add1 = {
    print(a+b)
}
add1() //2
a = 2
b = 3
add1() //5


//capture
let add2 = {[a,b] in
    print(a+b)
}
add2() //5
a = 3
b = 4
add2() //is 5, not 7. add2 capture a and b's value