ios - Can I cast Int64 directly into Int? -

i've been using sqlite.swift lately build app database. , i'm defining integer columns int64 type, documentation explains.

but every once in while need int64 int. question is, if this:

//create table int instead of int64 let test_id = expression<int>("test_id") let tests = db["tests"]  db.create(table: tests, ifnotexists: true){ t in     t.column(test_id) }   class func inserttest(t: int) -> int{     //insert.rowid returns int64 type     let insert = tests.insert(test_id <- t)     if let rowid = insert.rowid{         //directly cast int64 int         return int(rowid)     }     return 0 } 

will correct?

of course tested it. , works, reading this question in stackoverflow

and seems have problem 32 bits devices...

if wrong, how can cast int64 int?

converting int64 int passing int64 value int initializer work on 64-bit machine, , crash on 32-bit machine if integer outside of range int32.min ... int32.max.

for safety use init(truncatingbitpattern) initializer convert value:

return int(truncatingbitpattern: rowid) 

on 64-bit machine, truncatingbitpattern nothing; int (which same size int64 anyway).

on 32-bit machine, throw away top 32 bits, zeroes, haven't lost data. long value fit 32-bit int, can without losing data. if value outside of range int32.min ... int32.max, change value of int64 fits in 32-bit int, not crash.

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you can see how works in playground. since int in playground 64-bit int, can explicitly use int32 simulate behavior of 32-bit system.

let i: int64 = 12345678901  // value bigger maximum 32-bit int  let j = int32(truncatingbitpattern: i)  // j = -539,222,987 let k = int32(i)                        // crash! 

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update swift 3

in addition init(truncating:) still works, swift 3 introduces failable initializers safely convert 1 integer type another. using init?(exactly:) can pass 1 type initialize another, , returns nil if initialization fails. value returned optional must unwrapped in usual ways.

for example:

let i: int64 = 12345678901  if let j = int32(exactly: i) {     print("\(j) fits int32") } else {     // initialization returned nil     print("\(i) large int32") } 

this allows apply nil coalescing operator supply default value if conversion fails:

// return 0 if rowid big fit int on device return int(exactly: rowid) ?? 0