add ex088 async 5 await

This commit is contained in:
Dave Gauer 2021-05-13 19:48:10 -04:00
parent be279c78f5
commit 110e556ae1
3 changed files with 55 additions and 0 deletions

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@ -430,6 +430,10 @@ const exercises = [_]Exercise{
.main_file = "087_async4.zig",
.output = "1 2 3 4 5",
},
.{
.main_file = "088_async5.zig",
.output = "Example Title.",
},
};
/// Check the zig version to make sure it can compile the examples properly.

47
exercises/088_async5.zig Normal file
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@ -0,0 +1,47 @@
//
// Sure, we can solve our async value problem with a global
// variable. But this hardly seems like an ideal solution.
//
// So how do we REALLY get return values from async functions?
//
// The 'await' keyword waits for an async function to complete
// and then captures its return value.
//
// fn foo() u32 {
// return 5;
// }
//
// var foo_frame = async foo(); // invoke and get frame
// var value = await foo_frame; // await result using frame
//
// The above example is just a silly way to call foo() and get 5
// back. But if foo() did something more interesting such as wait
// for a network response to get that 5, our code would pause
// until the value was ready.
//
// As you can see, async/await basically splits a function call
// into two parts:
//
// 1. Invoke the function ('async')
// 2. Getting the return value ('await')
//
// Also notice that a 'suspend' keyword does NOT need to exist in
// a function to be called in an async context.
//
// Please use 'await' to get the string returned by
// getPageTitle().
//
const print = @import("std").debug.print;
pub fn main() void {
var myframe = async getPageTitle("http://example.com");
var value = ???
print("{s}\n", .{value});
}
fn getPageTitle(url: []const u8) []const u8 {
// Please PRETEND this is actually making a network request.
return "Example Title.";
}

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@ -0,0 +1,4 @@
39c39
< var value = ???
---
> var value = await myframe;