Describe the method of preparation of aldehydes from nitrile and ester compounds by reaction with $DIBAL-H$.

(N/A) $DIBAL-H$ stands for diisobutylaluminium hydride,$AlH(i-Bu)_2$.
$(a)$ Preparation of aldehyde from nitriles:
Nitriles are selectively reduced by $DIBAL-H$ to imines,which upon hydrolysis yield the corresponding aldehydes.
$R-CN \xrightarrow[(ii) H_2O]{(i) DIBAL-H} R-CHO$
$(b)$ Preparation of aldehyde from esters:
Esters are selectively reduced by $DIBAL-H$ to aldehydes.
$R-COOR' \xrightarrow[(ii) H_2O]{(i) DIBAL-H} R-CHO + R'OH$
Example reaction for ester:
$CH_3(CH_2)_9-CO-OC_2H_5 \xrightarrow[(ii) H_2O]{(i) DIBAL-H} CH_3(CH_2)_9-CHO$