Swift Learning Note (1): Assertion (assertions)

Assertion (assertions)

Optionals allows us to detect whether a value exists. In some cases, if a value does not exist or does not provide a specific satisfying condition, the code should not continue to execute down.

In these cases, you can use the trigger assertion to terminate execution and provide debugging.

The assertion is whether the condition is true at run time, and if true, continue down or it will be interrupted here.

assert that the corresponding keyword is assert

Such as:

Let-age =  //Here The result of the age >= 18 expression is true, so here the assertion does nothing, the code continues to perform  assert (age >=, "A-person ' A-age cannot is less than eighteen ")//  Here The result of the age >= 22 expression is false, so there will be an interrupt, print out  //" A person ' s age cannot is less than "  a Ssert (Age >, "A" cannot is less than 22 ")  

When do I use assertions?

Use assertions when the following conditions are included:

1. When an integer subscript index is passed as a value to a parameter implemented by a custom index, but the subscript index value cannot be too low or too high, use an assertion

2, pass the value to the function but if this pass-through value is invalid, the function cannot complete the function when the assertion is used.

3, the optional value is currently nil, but the following code successfully executes the condition is that the value cannot be nil, using assertions

Swift Learning Note (1): Assertion (assertions)