Study Notes 10 (Block) of swift Language)

Fengsh998 original address: Sorry!

In the previous studies, the closure was originally understood as a block. Although there are many similarities, the block still has its own uniqueness. Recently, when writing OC/SWIFT mixed encoding, sometimes swift calls back OC and OC calls back Swift.

Therefore, I will summarize the common statements and statements of block in swift. So that you do not forget it later. There is not much nonsense. The example above:

//// Blockdemo. swift // swiftdemo /// created by Apple on 14-6-29. // copyright (c) February 11, 2014 fensh. all rights reserved. // import Foundation // No parameter no return value typealias funcblock = ()-> () // or ()-> void // the return value is stringtypealias funcblocka = (INT, INT) -> string // the return value is a function pointer. The input parameter is stringtypealias funcblockb = (INT, INT)-> (string)-> () // the return value is a function pointer, if the input parameter is string, the returned value is also stringtypealias funcblockc = (INT, INT)-> (string)-> stringcl Ass blockdemo {// block as the property variable VAR blockproperty: (INT, INT)-> string = {, B In return ""/** // With initialization method var blockpropertynoreturn: (string)-> () = {Param in} var blockpropertya: funcblocka? // This method can be used for nil at the beginning, because the (ideal) state in the lifecycle may be nil? VaR blockpropertyb: funcblockb! // This statement can also be nil at the beginning, because the (ideal) state in the lifecycle is considered impossible to be nil, so it is used! Init () {println ("blockpropertya = \ (blockpropertya), blockpropertyb = \ (blockpropertyb)") println ("blockproperty = \ (blockproperty), blockpropertynoreturn = \ (blockpropertynoreturn) ")} func testproperty (Tag: INT) {Switch (TAG) {Case 1: Self. blockpropertynoreturn ("OK good") Case 2: If let exsistblock = self. blockpropertya {Let result = self. blockpropertya! (7,8) println ("result = \ (result)")} Case 3: If let exsistblock = self. blockpropertyb {Let fc = self. blockpropertyb (1, 2) FC ("output")} default: Let ret = self. blockproperty (3, 4) println (RET) }}// block as the function parameter func testblock (blockfunc: funcblock !) // Use! {If let exsistblock = blockfunc {blockfunc () // No parameter is returned} func testblocka (blockfunc: funcblocka !) {If let exsistblock = blockfunc {Let retstr = blockfunc (5, 6) println (retstr)} func testblockb (blockfunc: funcblockb !) {If let exsistblock = blockfunc {Let retfunc = blockfunc (5, 6) retfunc ("result is")} func testblockc (blockfunc: funcblockc !) {If let exsistblock = blockfunc {Let retfunc = blockfunc (5, 6) Let STR = retfunc ("the final result is") println (STR )}}}

Run the test code:

VaR BK = blockdemo () // no BK is output before block is set. testproperty (0) BK. testproperty (1) BK. testproperty (2) BK. testproperty (3) println ("================== set block attributes ===========================") BK. blockproperty = {(A: int, B: INT)-> string in let C = A * 100 + B Return "\ (a) * 100 + \ (B) = \ (c) "} BK. testproperty (0) BK. blockpropertynoreturn = {(Param: string)-> () in println ("input Param value is: \ (PARAM)")} BK. testproperty (1) BK. blockpropertya = {(A: int, B: INT)-> string in let C = A * 100 + B * 200 return "\ (a) * 100 + \ (B) * 200 = \ (c) "} BK. testproperty (2) BK. blockpropertyb = {(A: int, B: INT)-> (string)-> () in func sumprint (Result: string) {Let C = A + B; println ("sumprint func print: parame: \ (result) \ (A) + \ (B) = \ (c)")} return sumprint} BK. testproperty (3) println ("================= attribute block completion ============================= ") println ("================= when the function block is nil, no output ====================== ") BK. testblock (NiL) BK. testblocka (NiL) BK. testblockb (NiL) BK. testblockc (nil) println ("================= function block operations ============================") BK. testblock ({// do something println ("No parameter, no return value, block execution")}) BK. testblocka ({(A: int, B: INT)-> string in let C = A * 400 + B * 1000 return "\ (a) * 400 + \ (B) * 1000 is \ (c) "}) BK. testblockb ({(A: int, B: INT)-> (string)-> () in func sumprint (Result: string) {Let C = A/B; println ("sumprint func print: parame: \ (result) \ (a)/\ (B) = \ (c)")} return sumprint}) BK. testblockc ({(A: int, B: INT)-> (string)-> string in func sumrsult (Res: string) -> string {Let C = A * A + B * a return "\ (RES) \ (a) * \ (A) + \ (B) * \ () = \ (c) "} return sumrsult })

The block statements and usage
The output result is as follows:

Blockpropertya = nil, blockpropertyb = nilblockproperty = (function), blockpropertynoreturn = (function) ================== set block attributes ============================= 3*100 + 4 = 304 input Param value is: OK goodresult = 7*100 + 8*200 = 2300 sumprint func print: parame: output 1 + 2 = 3 ===================== attribute block completion ============================== =============== no output when the function block is nil ======================= ============ function block operations ====================== No parameter No Return Value block execution 5*400 + 6*1000 is 8000 sumprint func print: parame: The result is 5/6 = 0. The final result is 5*5 + 6*5 = 55.

Well, I think this is clearer than the description of the text. If you have any questions or other strange statements, you are welcome to kick off the gym .....